Magazine Articles |
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A. Klisnick. (2010). 50 ans du laser : Le laser aux extrémités du spectre : le laser X. Photoniques, 46, 52.
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Peer-reviewed Publications |
Alata, I., Dedonder, C., Broquier, M., Marceca, E., & Jouvet, C. (2010). Role of the charge-transfer state in the electronic absorption of protonated hydrocarbon molecules. J Am Chem Soc, 132(49), 17483–17489.
Résumé: The vibrationally resolved electronic spectra of isolated protonated polycyclic aromatic hydrocarbons (PAHs)-naphthalene, anthracene, and tetracene-have been recorded via neutral photofragment spectroscopy. The S1<--S0 transitions are all in the visible region and do not show a monotonic red shift as a function of the molecular size, as observed for the neutral analogues. Comparison with ab initio calculations indicates that this behavior is due to the nature of the excited state, which has a pronounced charge-transfer character for protonated linear PAHs with an even number of aromatic rings.
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Alata, I., Omidyan, R., Broquier, M., Dedonder, C., Dopfer, O., & Jouvet, C. (2010). Effect of protonation on the electronic structure of aromatic molecules: naphthaleneH+. Phys Chem Chem Phys, 12(43), 14456–14458.
Résumé: Protonated naphthalene, the smallest protonated polycyclic aromatic hydrocarbon cation, absorbs in the visible, around 500 nm, which corresponds to an unusually large red shift with respect to the neutral naphthalene counterpart.
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Albrecht, M., Borba, A., Le Barbu-Debus, K., Dittrich, B., Fausto, R., Grimme, S., Mahjoub, A., Nedic, M., Schmitt, U., Schrader, L., Suhm, M. A., Zehnacker-Rentien, A., & Zischang, J. (2010). Chirality influence on the aggregation of methyl mandelate. NEW JOURNAL OF CHEMISTRY, 34(7), 1266–1285.
Résumé: The methyl ester of mandelic acid is investigated by a wide range of techniques to unravel its aggregation pattern and the influence of relative chirality of the aggregating monomers. Matrix isolation confirms that a single monomer conformation prevails. The electronic spectrum of the dimers is strongly affected by the relative monomer chirality. Vibrational effects are more subtle and can be explained in terms of the most stable homo- and heteroconfigurational dimer structures, when compared to results of MP2 and DFT-D computations. Selective IR/UV double resonance techniques and wide-band FTIR spectroscopy provide largely consistent spectroscopic fingerprints of the chirality discrimination phenomena. The dominant homochiral dimer has two intermolecular O-H center dot center dot center dot O=C hydrogen bonds whereas the more strongly bound heterochiral dimer involves only one such hydrogen bond. This is a consequence of the competition between dispersion and intramolecular or intermolecular hydrogen bonding. Aromatic interactions also play a role in trimers and larger clusters, favoring homochiral ring arrangements. Analogies and differences to the well-investigated methyl lactate system are highlighted. Bulk phases show a competition between different hydrogen bond patterns. The enantiopure, racemic, and 3 : 1 crystals involve infinite hydrogen-bonded chains with different arrangements of the aromatic groups. They exhibit significantly different volatility, the enantiopure compound being more volatile than the racemic crystal. The accumulated experimental and quantum-chemical evidence turns methyl mandelate into a model system for the role of competition between dispersion forces and hydrogen bond interactions in chirality discrimination.
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Albrieux, F., Calvo, F., Chirot, F., Vorobyev, A., Tsybin, Y. O., Lepere, V., Antoine, R., Lemoine, J., & Dugourd, P. (2010). Conformation of Polyalanine and Polyglycine Dications in the Gas Phase: Insight from Ion Mobility Spectrometry and Replica-Exchange Molecular Dynamics. JOURNAL OF PHYSICAL CHEMISTRY A, 114(25), 6888–6896.
Résumé: The conformation of model [Arg(Ala)(4)X(Ala)(4)Lys+2H](2+) and [Arg(Gly)(4)X(Gly)(4)Lys+2H](2+) peptides has been systematically investigated as a function of the central amino acid X through a combined experimental and theoretical approach. Mass spectrometry-based ion mobility measurements have been performed together with conformational sampling using replica-exchange molecular dynamics to probe the influence of each amino acid on the stable peptide conformation. Satisfactory agreement is obtained between measured and calculated diffusion cross section distributions. The results confirm the propensity of alanine-based peptides to form a-helices in the gas phase, differences between peptides arising from the local arrangement of the central side chain with respect to the charged ends. More generally, we find that charge solvation plays a major role in secondary structure stabilization, especially in the case of glycine-based peptides. The rich variety of conformations exhibited by the latter is qualitatively captured by the simulations. This work illustrates the potentiality of such combined experimental/theoretical strategy to determine peptide secondary structures. The present polyalanine and polyglycine peptides also offer a series of benchmark systems for future conformation-resolved studies.
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Alchab, L., Dupuis, G., Balleyguier, C., Mathieu, M. - C., Fontaine-Aupart, M. - P., & Farcy, R. (2010). Towards an optical biopsy for the diagnosis of breast cancer in vivo by endogenous fluorescence spectroscopy. JOURNAL OF BIOPHOTONICS, 3(5-6), 373–384.
Résumé: The techniques of medical imaging allow the detection of suspect lesions in the breast, but they do not always evidence the malignant nature of these lesions. Breast biopsies and histological analyses are therefore implemented to establish a diagnosis. In order to reduce the number of these invasive procedures, a portable clinical system was designed based upon the excitation of Endogenous Fluorescence in vivo at 405 nm via a fiber-optics probe included in a disposable needle of small diameter (<1 mm). From the fluorescence signal, the authors are able to discriminate between diseased and healthy areas of human breast biopsies. Stronger fluorescence intensity and systematic spectral red shift of the tumor areas were observed. These results are confirmed by confocal microscopy. This new instrument is promising for the minimally invasive diagnosis of breast tumors in vivo with an appreciable limitation of patient trauma and of operational and financial cost. [GRAPHICS] Measurement of the endogenous fluorescence spectrum of a tissue sample via a fiber-optics probe included in a disposable needle of small diameter (<1 mm).
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Anne Zehnacker Ed. (2010). Chiral Recognition in the Gas Phase. CRC Press Taylor & Francis Group, .
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Anouchah Momeni, P. S., Patrick Rousseau, Hocine Khemliche, and Philippe Roncin. (2010). Grazing Incidence Fast Atom Diffraction (GIFAD): Doing RHEED with Atoms. e-J. Surf. Sci. Nanotech, 8, 101–104.
Résumé: We describe a new diffraction technique to investigate the surface of single crystal surfaces. Its geometry is the
same as that of the RHEED technique. In GIFAD, instead of 10-30 keV electrons, the projectiles are neutral atoms
(mainly helium) with energies in the keV range. We present few results obtained with GIFAD highlighting the
simplicity of interpretation.
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Atabek, O., & Lefebvre, R. (2010). Laser Control of Vibrational Transfer Based on Exceptional Points†. JOURNAL OF PHYSICAL CHEMISTRY A, 114, 3031.
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Aubry, G., Meance, S., Haghiri-Gosnet, A. - M., & Kou, Q. (2010). Flow rate based control of wavelength emission in a multicolor microfluidic dye laser. MICROELECTRONIC ENGINEERING, 87(5-8), 765–768.
Résumé: An original method is investigated to monitor the emission of a microfluidic dye laser. It relies on the flow rate of a dye mixture solution. The two dyes are at the origin of laser effects at two distinct wavelengths. In function of the dye mixture flow rate, one wavelength or the other can be selected. The purpose is to achieve a wavelength on-demand system which would be of great interest for spectroscopic analysis of biochemical samples. (C) 2009 Elsevier B.V. All rights reserved.
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Aufray, B., Kara, A., Vizzini, S., Oughaddou, H., Leandri, C., Ealet, B., & Le Lay, G. (2010). Graphene-like silicon nanoribbons on Ag(110): A possible formation of silicene. APPLIED PHYSICS LETTERS, 96(18), 183102.
Résumé: Scanning tunneling microscopy (STM) and ab initio calculations based on density functional theory (DFT) were used to study the self-aligned silicon nanoribbons on Ag(110) with honeycomb, graphene-like structure. The silicon honeycombs structure on top of the silver substrate is clearly observed by STM, while the DFT calculations confirm that the Si atoms adopt spontaneously this new silicon structure. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3419932]
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Basire, M., Parneix, P., & Calvo, F. (2010). Finite-Temperature IR Spectroscopy of Polyatomic Molecules: A Theoretical Assessment of Scaling Factors. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3139–3146.
Résumé: With I recently developed simulation method (Basire, M; et al. J. Phys. Chem A 2009, 113, 6947), the infrared vibrational spectra of several polyatomic molecules are calculated over I broad range of temperature, taking into account quantum, anharmonic, and couplings effects. Anharmonic force fields, generated from static first-principle calculations, are Sampled in the microcanonical ensemble to provide energy-resolved absorption intensities and their finite temperature analogues after Laplace transformation Effective anharmonic frequencies ire characterized as a continuous function of temperature for vinyl fluoride, the N-acetyl-Phe-NH(2) peptide. and protonated naphthalene. These frequencies generally deviate increasingly from the harmonic value with increasing temperature although the overestimation due to the harmonic approximation is particularly Salient for high-frequency Modes Anharmonicities may also be sufficient 10 alter structural assignment of experimental spectra experimental spectra with respect to empirically scaled harmonic bands. These results, emphasize some possible limatations and inaccuractes, Inherent to such static Scaling factors for correcting harmonic IR Spectra.
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Bellec, A., Riedel, D., Dujardin, G., Boudrioua, O., Chaput, L., Stauffer, L., & Sonnet, P. (2010). Nonlocal Activation of a Bistable Atom through a Surface State Charge-Transfer Process on Si(100)-(2 x 1):H. Phys. Rev. Lett., 105(4), 048302.
Résumé: The reversible hopping of a bistable atom on the Si(100)-(2 x 1):H surface is activated nonlocally by hole injection into Si-Si bond surface states with a low temperature (5 K) scanning tunneling microscope. In the contact region, at short distances (<1.5 nm) between the hole injection site and the bistable atom, the hopping yield of the bistable atom exhibits remarkable variations as a function of the hole injection site. It is explained by the density of state distribution along the silicon bond network that shows charge-transfer pathways between the injection sites and the bistable atom.
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Bergeron, H., Gazeau, J. - P., Siegl, P., & Youssef, A. (2010). Semi-classical behavior of Poschl-Teller coherent states. EPL, 92(6), 60003.
Résumé: We present a construction of semi-classical states for Poschl-Teller potentials based on a supersymmetric quantum mechanics approach. The parameters of these “coherent” states are points in the classical phase space of these systems. They minimize a special uncertainty relation. Like standard coherent states they resolve the identity with a uniform measure. They permit to establish the correspondence (quantization) between classical and quantum quantities. Finally, their time evolution is localized on the classical phase space trajectory. Copyright (C) EPLA, 2010
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Bernhardt, B., Ozawa, A., Jacquet, P., Jacquey, M., Kobayashi, Y., Udem, T., Holzwarth, R., Guelachvili, G., Haensch, T. W., & Picque, N. (2010). Cavity-enhanced dual-comb spectroscopy. NATURE PHOTONICS, 4(1), 55–57.
Résumé: The sensitivity of molecular fingerprinting is dramatically improved when the absorbing sample is placed in a high-finesse optical cavity, because the effective path length is increased. When the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace gases may be identified(1) within a few milliseconds. However, efficient analysis of the light transmitted through the cavity remains challenging. Here, a novel approach-cavity-enhanced, frequency-comb, Fourier-transform spectroscopy-fully overcomes this difficulty and enables measurement of ultrasensitive, broad-bandwidth, high-resolution spectra within a few tens of microseconds without any need for detector arrays, potentially from the terahertz to ultraviolet regions. Within a period of just 18 μs, we recorded the spectra of the ammonia 1.0 μm overtone bands comprising 1,500 spectral elements and spanning 20 nm, with a resolution of 4.5 GHz and a noise equivalent absorption at 1 s averaging of 1 x 10(-10) cm(-1) Hz(-1/2), thus opening a route to time-resolved spectroscopy of rapidly evolving single events.
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Bernhardt, B., Sorokin, E., Jacquet, P., Thon, R., Becker, T., Sorokina, I. T., Picque, N., & Haensch, T. W. (2010). Mid-infrared dual-comb spectroscopy with 2.4 μm Cr2+:ZnSe femtosecond lasers. APPLIED PHYSICS B-LASERS AND OPTICS, 100(1), 3–8.
Résumé: The mid-infrared part of the electromagnetic spectrum is the so-called molecular fingerprint region because gases have tell-tale absorption features associated with molecular rovibrations. This region can be for instance exploited to detect small traces of environmental and toxic vapors in atmospheric and industrial applications. Novel Fourier-transform spectroscopy without moving parts, based on time-domain interferences between two comb sources, can in particular benefit optical diagnostics and precision spectroscopy. To date, high-resolution and -sensitivity proof-of-principle experiments have only been reported in the near-infrared region where frequency-comb oscillators are conveniently available. However, as most of the molecular transitions in this region are due to weak overtone bands, this spectral domain is not ideal for sensitive and rapid detection. Here we present a proof-of-principle experiment of frequency-comb Fourier-transform spectroscopy with two Cr2+:ZnSe femtosecond oscillators directly emitting in the 2.4 μm mid-infrared region. The acetylene absorption spectrum in the region of the nu(1)+nu 1/5 band, extending from 2370 to 2525 nm, could be recorded within a 10 μs acquisition time without averaging with 12 GHz resolution.
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Bobrov, K., & Guillemot, L. (2010). Strain engineering tunable nanotemplates on the Cu(110)-(2 x 1)-O surface. SURFACE SCIENCE, 604(21-22), 1894–1898.
Résumé: We present an STM study on the domain pattern formation of the Cu(110)-O surface. We found that the separation of the oxygen adsorbate phase into the domain pattern is consistent with a phenomenological model of size-dependent elastic relaxation of the strained surface. We developed a thermally assisted oxygen adsorption procedure aiming to control the size of the two-dimensional (2x1)-O islands nucleated at the surface under oxygen adsorption serving as precursors for domain pattern formation. We engineered wide range tuneable (2x1)-O domain patterns by controlling the nuclei size and the oxygen coverage at the pattern formation stage. (C) 2010 Elsevier B.V. All rights reserved.
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Boer-Duchemin, E., Tranvouez, E., & Dujardin, G. (2010). The interaction of an atomic force microscope tip with a nano-object: a model for determining the lateral force. Nanotechnology, 21(45), 455704.
Résumé: A calculation of the lateral force interaction between an atomic force microscope (AFM) tip and a nano-object on a substrate is presented. In particular, the case where the AFM tip is used to manipulate the nano-object is considered; i.e., the tip is displaced across the nano-object with the feedback off. The Hamaker equations are used to calculate the force when the tip and sample are not in contact and the Johnson, Kendall and Roberts (JKR) or Derjaguin, Muller and Toporov (DMT) formalisms are used for the contact force. The effect of the material parameters, the choice of contact theory and the shape of the nano-object on the resulting lateral forces are explored. The calculation is applied to an experimental system consisting of a cadmium selenide nanorod on graphite.
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Boudon, V., Pirali, O., Roy, P., Brubach, J. B., Manceron, L., & Auwera, J. V. (2010). The high-resolution far-infrared spectrum of methane at the SOLEIL synchrotron. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 111(9), 1117–1129.
Résumé: As a tetrahedral molecule, methane has no permanent dipole moment. Its spectrum, however, displays faint absorption lines in the THz region, due to centrifugal distorsion effects. This is important for planetary applications since this region is used to measure methane concentration in some planetary atmospheres, in particular on Titan. Up to now, all measurements relied either on some old low resolution infrared absorption spectra, or on high resolution Stark measurements for low J values only. Even if these results have been reexamined recently [Wishnow EH, Orton GS, Ozier I. Gush HP. The distorsion dipole rotational spectrum of CH(4): a low temperature far-infrared study.J Quant Spectrosc Radiat Transfer 2007:103:102-17], it seemed highly desirable to obtain much more precise laboratory data. The high-intensity synchrotron radiation, combined with a 151.75 +/- 0.1 m optical path in a White cell and a Bruker IFS 125 HR FTIR spectrometer at the AILES beamline of SOLEIL, enabled us to record this very weak spectrum at high resolution for the first time. Spectra were obtained in the 50-500 cm(-1) wavenumber range at 296K and 9.91, 20, 50 and 100 mbar with a resolution of 0.00074, 0.00134, 0.0034 and 0.0067 cm(-1) (FWHM of the sinc function), respectively. The rotational clusters are fully resolved and the good signal-to-noise ratio has enabled precise measurements of transition intensities (92 cold band lines and 96 Dyad-Dyad hot band lines, with normal abundance intensities in the range 2 x 10(-26)-1 x 10(-24) cm(-1) /(mol cm(-2))), yielding an accurate determination of the dipole moment derivatives. Such results should allow a better determination of CH(4) concentration in planetary objects. (C) 2010 Elsevier Ltd. All rights reserved.
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Calvo, F., Basire, M., & Parneix, P. (2010). Efficiency of Monte Carlo methods for densities and sums of rovibrational states. CHEMICAL PHYSICS LETTERS, 496(1-3), 196–200.
Résumé: Absolute quantum densities of rovibrational states of fully coupled Hamiltonians are computed using Wang-Landau, virtual-move parallel tempering (VMPT), and the Bortz-Kalos-Lebowitz (or kMC) Monte Carlo methods. The validity of the methods is checked by comparing to exact counting in the case of the H(2)SiO molecule, but applications are also presented for vinyl fluoride and neutral naphthalene. The numerical efficiencies obtained by measuring the statistical deviation to the converged value under finite sampling times suggest that the Wang-Landau and kMC methods are generally superior to VMPT for this class of problem. A simple application to isomerization in protonated pyrene is presented. (C) 2010 Elsevier B.V. All rights reserved.
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Calvo, F., Parneix, P., & Van-Oanh, N. - T. (2010). Finite temperature infrared spectroscopy of polycyclic aromatic hydrocarbon molecules: Path-integral molecular dynamics. JOURNAL OF CHEMICAL PHYSICS, 132(12), 124308.
Résumé: The vibrational spectra of the naphthalene, pyrene, and coronene molecules have been computed in the 0-3500 cm(-1) infrared range using classical and quantum molecular dynamics simulations based on a dedicated tight-binding potential energy surface. The ring-polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (CMD) methods have been employed to account for quantum nuclear effects. The contributions of quantum delocalization to the line shift and broadening are significant in the entire spectral range and of comparable magnitude as pure thermal effects. While the two methods generally produce similar results, the CMD method may converge slower at low temperature with increasing Trotter discretization number. However, and contrary to the CMD method, the RPMD approach suffers from serious resonance problems at high frequencies and low temperatures.
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Calvo, F., Parneix, P., & Van-Oanh, N. - T. (2010). Finite-temperature infrared spectroscopy of polycyclic aromatic hydrocarbon molecules. II. Principal mode analysis and self-consistent phonons. JOURNAL OF CHEMICAL PHYSICS, 133(7), 074303.
Résumé: Following previous work [F. Calvo et al. J. Chem. Phys. 132, 124308 (2010)], infrared spectra of several polycyclic aromatic hydrocarbon molecules are simulated with classical and quantum molecular dynamics trajectories. The interactions are modeled using a tight-binding potential energy surface and quantum delocalization is accounted for using the partially adiabatic centroid and ring-polymer molecular dynamics frameworks, both built upon the path-integral representation. The spectra obtained directly by Fourier transformation of the dipole moment autocorrelation function are here compared with several quasiharmonic approximations that provide additional information about the vibrational modes. A principal mode analysis (PMA) is carried out from the covariance matrix of atomic displacements in classical and quantum trajectories. The method systematically overestimates the line shifts due to anharmonicities, except in the power spectra of atomic displacements, and is not robust in predicting IR intensities for such large molecules. Alternatively, effective normal modes have also been determined by adapting the self-consistent phonon (SCP) theory of condensed matter physics to the present tight-binding model, in both classical and quantum mechanical descriptions. The SCP approximation turns out as semiquantitative in estimating the redshift of tight stretching modes, and performs better for classical systems. More problematic, it predicts that many low-or medium-frequency modes should be blueshifted, in contradiction with the molecular dynamics results. The sets of anharmonic normal modes extracted from the PMA and SCP approaches reveal important mixings within the tightest C-H and C-C stretching modes, which are also manifested on the corresponding power spectra. (C) 2010 American Institute of Physics. [doi:10.1063/1.3465554]
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Ceponkus, J., Chin, W., Chevalier, M., Broquier, M., Limongi, A., & Crepin, C. (2010). Infrared study of glycolaldehyde isolated in parahydrogen matrix. JOURNAL OF CHEMICAL PHYSICS, 133(9), 094502.
Résumé: The infrared spectrum of glycolaldehyde sugar model in solid parahydrogen is reported and interpreted in the light of ab initio anharmonic frequency calculations. The advantages of parahydrogen lead to a simplification of its infrared spectroscopy compared to other conventional matrices. Surprisingly, the sugar molecule is found to display an unexpected large bandwidth compared to the smaller organic molecules studied in parahydrogen so far. Among them, only glycolaldehyde possesses an internal hydrogen-bond. Band broadening in glycolaldehyde is interpreted as originating mainly from the presence of the hydrogen-bond and to a lesser extent from clustering with oH(2) impurities. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3474994]
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Chabot, M., Mezdari, F., Beroff, K., Martinet, G., & Hervieux, P. - A. (2010). Scaling Law for the Partitioning of Energy in Fragmenting Multicharged Carbon Clusters. PHYSICAL REVIEW LETTERS, 104(4), 043401.
Résumé: The complete fragmentation of highly excited and multicharged C(n)(q+) clusters (n = 5-10; q = 2-4), produced in high velocity collisions of C(n)(+) with atoms, has been measured. Multiplicity distributions are presented and used to deduce, within a statistical framework, the partitioning of energy between the fragments' production and fragments' kinetic energy. This partitioning is found to scale as the charge over mass ratio of the cluster.
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Chabot, M., Tuna, T., Beroff, K., Pino, T., Le Padellec, A., Desesquelles, P., Martinet, G., Nguyen-Thi, V. O., Carpentier, Y., Le Petit, F., Roueff, E., & Wakelam, V. (2010). Statistical universal branching ratios for cosmic ray dissociation, photodissociation, and dissociative recombination of the Cn=2-10, Cn=2-4H and C3H2 neutral and cationic species. ASTRONOMY & ASTROPHYSICS, 524, A39.
Résumé: Context. Fragmentation-branching ratios of electronically excited molecular species are of first importance for the modeling of gas phase interstellar chemistry. Despite experimental and theoretical efforts that have been done during the last two decades there is still a strong lack of detailed information on those quantities for many molecules such as C-n, CnH or C3H2. Aims. Our aim is to provide astrochemical databases with more realistic branching ratios for C-n (n = 2 to 10), CnH (n = 2 to 4), and C3H2 molecules that are electronically excited either by dissociative recombination, photodissociation, or cosmic ray processes, when no detailed calculations or measurements exist in literature. Methods. High velocity collision in an inverse kinematics scheme was used to measure the complete fragmentation pattern of electronically excited C-n (n = 2 to 10), CnH (n = 2 to 4), and C3H2 molecules. Branching ratios of dissociation where deduced from those experiments. The full set of branching ratios was used as a new input in chemical models and branching ratio modification effects observed in astrochemical networks that describe the dense cold Taurus Molecular Cloud-1 and the photon dominated Horse Head region. Results. The comparison between the branching ratios obtained in this work and other types of experiments showed a good agreement. It was interpreted as the signature of a statistical behavior of the fragmentation. The branching ratios we obtained lead to an increase of the C-3 production together with a larger dispersion of the daughter fragments. The introduction of these new values in the photon dominated region model of the Horse Head nebula increases the abundance of C-3 and C3H, but reduces the abundances of the larger C-n and hydrocarbons at a visual extinction AV smaller than 4. Conclusions. We recommend astrochemists to use these new branching ratios. The data published here have been added to the online database KIDA (KInetic Database for Astrochemistry, http://kida.obs.u-bordeaux1.fr).
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Chakraborty, A., Le Barbu-Debus, K., Zehnacker-Rentien, A., & Guchhait, N. (2010). Laser-induced fluorescence and dispersed fluorescence studies of the donor-acceptor system 4-amino 3-methyl benzoic acid methyl ester and its solvated clusters: Evidence of excited-state charge-transfer reaction. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 213(2-3), 164–170.
Résumé: Laser-induced fluorescence (LIF) excitation and dispersed fluorescence (OF) spectra of 4-amino 3-methyl benzoic acid methyl ester (AMBME) and its solvated clusters with solvents such as methanol, water and acetonitrile have been investigated in a supersonic expansion. Spectral signature supports the presence of two conformers in the cooled jet which is in line with theoretical calculations. In addition to structured local emission from the Franck Condon excited state, the molecule AMBME shows red-shifted broad emission from the state attributed to the close-lying charge transfer (CT) state, which is facilitated by exciting low-frequency modes. The molecule readily forms clusters with different solvents and the clusters' electronic excitation bands appear in the low-energy side of the transition origin of the bare molecule. Excitation of the clusters leads to the appearance of red-shifted solvent-polarity dependent CT emission. (C) 2010 Elsevier B.V. All rights reserved.
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Champeaux, J. P., Carcabal, P., Rabier, J., Cafarelli, P., Sence, M., & Moretto-Capelle, P. (2010). Dehalogenation of 5-halo-uracil molecules induced by 100 keV proton collisions. Phys. Chem. Chem. Phys., 12(20), 5454–5461.
Résumé: Neutral and cationic halogen loss of singly and doubly ionised 5-X-uracil (X = F, Cl, Br, I) after collisions with 100 keV protons have been studied in the gas phase. The rates of these dissociation channels are strongly dependant on the nature of the halogen substituent. It is very weak in the case of fluorine but is a dominant channel for iodine. Dissociation mechanisms are proposed for a number of significant channels associated to dehalogenation. It is suggested that some final ion products originate from specific processes. For instance, ion products of mass 38, 39 and 40 amu are very sensitive to the nature of the primarily ejected halogen and result from pathways associated to dehydrogenation and transient formation of the dehalogenated uracil cation.
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Chen, L., Valdes, J. E., Vargas, P., & Esaulov, V. A. (2010). Surface channelling and energy losses of 4 keV hydrogen and fluorine ions in grazing scattering on Au(111) and missing row reconstructed Au(110) surfaces. Journal of physics, 22(34), 345005.
Résumé: We present the results of an experimental and theoretical study of surface channelling and energy loss of 4 keV hydrogen and fluorine ions in grazing scattering on a missing row reconstructed Au(110) surface and a Au(111) surface. We performed measurements of energy losses for grazing angle scattering in surface channelling conditions for various azimuthal orientations of the crystal. Experimental results are discussed in the light of trajectory calculations of hydrogen and fluorine ions scattered under grazing incidence conditions on the surface. A nonlinear model is used in order to calculate the ion energy loss in these crystalline systems. Ab initio electronic crystal structure calculations and semi-classical simulations are performed and allow us to delineate various trajectory classes that correspond to different contributions in the energy loss spectra for various azimuthal orientations of the surface.
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Chevalier, M., Broquier, M., & Brenner, V. (2010). Infrared study on hydrogen chloride complexed with allene. J. Chem. Phys., 132(16), 164306.
Résumé: The first rotationally resolved observation of the infrared (IR) spectrum of the molecular complex C(3)H(4)-HCl in gas phase is reported. New IR spectra have been recorded at high resolution by means of a slit jet. Rotational constants and vibrational frequencies have been obtained from these spectra. These data are presented and compared with high level ab initio calculations (CCSD(T)/cc-pVTZ). The results obtained in this study are compared with those on acetylene and ethene-HCl complexes. We observe a broadening of the lines interpreted as a decrease of the lifetime of the excited vibrational state with the size of the partner of complexation and also a correlation between the vibrational shift of the H-Cl stretching mode and the proton affinity of the acceptor molecule. (C) 2010 American Institute of Physics. [doi:10.1063/1.3397990]
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Crepin C., S. N., Chin W., Galaup J.P., M. C. J. G., & Arabei S.M. (2010). Emission stimulée par des molécules de tétrabenzoporphine en matrice de gaz rares à basse température. PROCEEDINGS of the VIII International Conference on “Quantum Electronics”, (Minsk, Belarus), 57.
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Crepin, C., Shafizadeh, N., Chin, W., Galaup, J. - P., McCaffrey, J. G., & Arabei, S. M. (2010). Unveiled optical properties of tetrapyrollic pigments in cryogenic environments. LOW TEMPERATURE PHYSICS, 36(5), 451–457.
Résumé: An unexpected phenomenon was revealed in the laser induced fluorescence spectra of free-base (H(2)Pc) and zinc (ZnPc) phthalocyanines trapped in rare gas and nitrogen matrices under a moderate increase in the laser intensity. In all matrices the intensity of an emission band near 755 nm increased drastically when pumping the S(1)<- S(0) transition. This observation was assigned to stimulated emission in a four-level scheme involving a vibronic transition from the lowest electronic state to a vibrational level of the ground state. In the present work, we expose new similar results obtained with porphyrin molecules, i.e. tetra-benzoporphin (TBP). With free-base H(2)TBP, stimulated emission was observed in Ar or N(2) matrices, but not in Xe matrices. A possible reason could be a fast inter-system crossing rate due to the heavy atom effect induced by Xe. We also report the observation of persistent burnt spectral holes, although the low efficiency of this process is not competitive with stimulated emission and no decrease of the stimulated emission with time was observed. With ZnTBP no stimulated emission could be recorded but the appearance of rather strong phosphorescence was noticed. Similar studies focusing on the stimulated emission phenomenon is that they should allow new insights into site effects and site selectivity. (C) 2010 American Institute of Physics.
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Cuisset, A., Nanobashvili, L., Smirnova, I., Bocquet, R., Hindle, F., Mouret, G., Pirali, O., Roy, P., & Sadovskii, D. A. (2010). Far-infrared high resolution synchrotron FTIR spectroscopy of the nu(11) bending vibrational fundamental transition of dimethylsulfoxyde. CHEMICAL PHYSICS LETTERS, 492(1-3), 30–34.
Résumé: We report the first successful high resolution gas phase study of the 'parallel' band of DMSO at 380 cm(-1) associated with the nu(11) bending vibrational mode. The spectrum was recorded with a resolution of 0.0015 cm(-1) using the AILES beamline of the SOLEIL synchrotron source, the IFS 125 FTIR spectrometer and a multipass cell providing an optical path of 150 m. The rotational constants and centrifugal corrections obtained from the analysis of the resolved rotational transitions reproduce the spectrum to the experimental accuracy. (C) 2010 Elsevier B.V. All rights reserved.
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de Miranda, B. K. C., Alcaraz, C., Elhanine, M., Noller, B., Hemberger, P., Fischer, I., Garcia, G. A., Soldi-Lose, H., Gans, B., Mendes, L. A. V., Boye-Peronne, S., Douin, S., Zabka, J., & Botschwina, P. (2010). Threshold Photoelectron Spectroscopy of the Methyl Radical Isotopomers, CH3, CH2D, CHD2 and CD3: Synergy between VUV Synchrotron Radiation Experiments and Explicitly Correlated Coupled Cluster Calculations. JOURNAL OF PHYSICAL CHEMISTRY A, 114(14), 4818–4830.
Résumé: Threshold photoelectron spectra (TPES) of the isotopomers of the methyl radical (CH3, CH2D, CHD2, and CD3) have been recorded in the 9.5-10.5 eV VUV photon energy range using third generation synchrotron radiation to investigate the vibrational spectroscopy of the corresponding cations at a 7-11 meV resolution. A threshold photoelectron-photoion coincidence (TPEPICO) spectrometer based on velocity map imaging and Wiley-McLaren time-of-flight has been used to simultaneously record the TPES of several radical species produced in a Ar-seeded beam by dc flash-pyrolysis of nitromethane (CHxDyNO2, x + y = 3). Vibrational bands belonging to the symmetric stretching and out-of-plane bending modes have been observed and P, Q, and R branches have been identified in the analysis of the rotational profiles. Vibrational configuration interaction (VCI), in conjunction with near-equilibrium potential energy surfaces calculated by the explicitly correlated coupled cluster method CCSD(T*)-F12a, is used to calculate vibrational frequencies for the four radical isotopomers and the corresponding cations. Agreement with data from high-resolution IR spectroscopy is very good and a large number of predictions is made. In particular, the calculated wavenumbers for the out-of-plane bending vibrations, v(2)(CH3+) = 1404 cm(-1), v(4)(CH2D+) = 1308 cm(-1), v(4)(CHD2+) = 1205 cm(-1), and v(2)(CD3+) = 1090 cm(-1), should be accurate to ca. 2 cm(-1). Additionally, computed Franck-Condon factors are used to estimate the importance of autoionization relative to direct ionization. The chosen models globally account for the observed transitions, but in contrast to PBS spectroscopy, evidence for rotational and vibrational autoionization is found. It is shown that state-selected methyl cations can be produced by TPEPICO spectroscopy for ion-molecule reaction studies, which are very important for the understanding of the planetary ionosphere chemistry.
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De Padova, P., Quaresima, C., Ottaviani, C., Sheverdyaeva, P. M., Moras, P., Carbone, C., Topwal, D., Olivieri, B., Kara, A., Oughaddou, H., Aufray, B., & Le Lay, G. (2010). Evidence of graphene-like electronic signature in silicene nanoribbons. APPLIED PHYSICS LETTERS, 96(26), 261905.
Résumé: We report on the electronic properties of straight, 1.6 nm wide, silicene nanoribbons on Ag(110), arranged in a one-dimensional grating with a pitch of 2 nm, whose high-resolution scanning tunneling microscopy images reveal a honeycomb geometry. Angle-resolved photoemission shows quantum confined electronic states of one-dimensional character. The silicon band dispersion along the direction of the nanoribbons suggests a behavior analogous to the Dirac cones of graphene on different substrates. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3459143]
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Dowek, D., Perez-Torres, J. F., Picard, Y. J., Billaud, P., Elkharrat, C., Houver, J. C., Sanz-Vicario, J. L., & Martin, F. (2010). Circular Dichroism in Photoionization of H-2. PHYSICAL REVIEW LETTERS, 104(23), 233003.
Résumé: Circular dichroism is a consequence of chirality. However, nonchiral molecules can also exhibit it when the measurement itself introduces chirality, e. g., when measuring molecular-frame photoelectron angular distributions. The few such experiments performed on homonuclear diatomic molecules show that, as expected, circular dichroism vanishes when the molecular-frame photoelectron angular distributions are integrated over the polar electron emission angle. Here we show that this is not the case in resonant dissociative ionization of H-2 for photons of 30-35 eV, which is the consequence of the delayed ionization from molecular doubly excited states into ionic states of different inversion symmetry.
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El Asri, T., Raissi, M., Vizzini, S., El Maachi, A., Ameziane, E. L., d'Avitaya, F. A., Lazzari, J. L., Coudreau, C., Oughaddou, H., Aufray, B., & Kaddouri, A. (2010). Inter-diffusion of cobalt and silicon through an ultra thin aluminum oxide layer. APPLIED SURFACE SCIENCE, 256(9), 2731–2734.
Résumé: Optical emission spectroscopy of sputtered species during ion bombardment, Auger electron spectroscopy and high-resolution transmission electron microscopy were used to study the cobalt and silicon diffusion through the interfaces of Co/AlO/Si(0 0 1) hetero-structure. The results are discussed as a function of the annealing temperature of sample and show that the diffusion process at the interfaces starts for annealing temperatures above 200 degrees C without detectable modification of the oxide layer. (C) 2009 Elsevier B. V. All rights reserved.
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Elkharrat, C., Picard, Y. J., Billaud, P., Cornaggia, C., Garzella, D., Perdrix, M., Houver, J. C., Lucchese, R. R., & Dowek, D. (2010). Ion Pair Formation in Multiphoton Excitation of NO2 Using Linearly and Circularly Polarized Femtosecond Light Pulses: Kinetic Energy Distribution and Fragment Recoil Anisotropy (vol 114A, pg 9902, 2010). JOURNAL OF PHYSICAL CHEMISTRY A, 114(50), 13288.
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Galue, H. A., Pirali, O., & Oomens, J. (2010). Gas-phase infrared spectra of cationized nitrogen-substituted polycyclic aromatic hydrocarbons. ASTRONOMY & ASTROPHYSICS, 517, A10.
Résumé: Gas-phase infrared spectra of several ionized nitrogen substituted polycyclic aromatic hydrocarbons (PANHs) have been recorded in the 600-1600 cm(-1) region via IR multiple-photon dissociation (IRMPD) spectroscopy. The UV photoionized PANH ions are trapped and isolated in a quadrupole ion trap where they are irradiated with an IR free electron laser. The PANHs were studied in their radical cation (PANH(+)) and protonated (H(+) PANH) forms, and include quinoline, isoquinoline, phenanthridine, benzo[h] quinoline, acridine, and dibenzo[f,h] quinoline. Experimental IRMPD spectra were interpreted with the aid of density functional theory methods. The PANH(+) IR spectra are found to resemble those of their respective non-nitrogenated PAH cations. The IR spectra of H(+) PANHs are significantly different owing to the NH inplane bending vibration, which generally couples very well with the aromatic CH bending and CC stretching modes. Implications of the NPAH (+, H(+)) laboratory spectra are discussed for the astrophysical IR emissions and, in particular, for the band at 6.2 μm.
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Gans, B., Mendes, L. A. V., Boye-Peronne, S., Douin, S., Garcia, G., Soldi-Lose, H., de Miranda, B. K. C., Alcaraz, C., Carrasco, N., Pernot, P., & Gauyacq, D. (2010). Determination of the Absolute Photoionization Cross Sections of CH3 and I Produced from a Pyrolysis Source, by Combined Synchrotron and Vacuum Ultraviolet Laser Studies. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3237–3246.
Résumé: A pyrolysis source coupled to a supersonic expansion has been used to produce the CH3 radical from two precursors, iodomethane CH3I and nitromethane CH3NO2. The relative ionization yield of CH3 has been recorded at the SOLEIL Synchrotron Radiation source in the range 9.0-11.6 eV, and its ionization threshold has been modeled by taking into account the vibrational and rotational temperature of the radical in the molecular beam. The relative photoionization yield has been normalized to an absolute cross section scale at a fixed wavelength (118.2 nm, sigma(CH3)(i) = 6.7(-1.8)(+2.4) Mb, 95% confidence interval) in an independent laboratory experiment using the same pyrolysis source, a vacuum ultraviolet (VUV) laser, and a carefully calibrated detection chain. The resulting absolute cross section curve is in good agreement with the recently published measurements by Taatjes et al.,((1)) although with an improved signal-to-noise ratio. The absolute photoionization cross section of CH3I at 118.2 nm has also been measured to be sigma(CH3I)(i) = (48.2 +/- 7.9) Mb, in good agreement with previous electron impact measurements. Finally, the photoionization yield of the iodine atom in its ground state P-2(3/2) has been recorded using the synchrotron source and calibrated for the first time on an absolute cross section scale from our fixed 118.2 nm laser measurement, sigma(I2P3/2)(i) = 74(-23)(+33) Mb (95% confidence interval). The ionization curve of atomic iodine is in good agreement, although with slight variations, with the earlier relative ionization yield measured by Berkowitz et al.((2)) and is also compared to an earlier calculation of the iodine cross section by Robicheaux and Greene.((3)) It is demonstrated that, in the range of pyrolysis temperature used in this work, all the ionization cross sections are temperature-independent. Systematic care has been taken to include all uncertainty sources contributing to the final confidence intervals for the reported results.
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Gauyacq, J. - P., Novaes, F. D., & Lorente, N. (2010). Magnetic transitions induced by tunneling electrons in individual adsorbed M-phthalocyanine molecules (M=Fe and Co). Phys. Rev. B, 81(16), 165423.
Résumé: We report on a theoretical study of magnetic transitions induced by tunneling electrons in individual adsorbed M-Phthalocyanine (M-Pc) molecules where M is a metal atom: Fe-Pc on a Cu(110)(2 x 1)-O surface and Co-Pc layers on Pb(111) islands. The magnetic transitions correspond to the change in orientation of the spin angular momentum of the metal ion with respect to the surroundings and possibly an applied magnetic field. The adsorbed Fe-Pc system is studied with a density-functional-theory-transport approach showing that (i) the magnetic structure of the Fe atom in the adsorbed Fe-Pc is quite different from that of the free Fe atom or of other adsorbed Fe systems and (ii) that injection of electrons (holes) into the Fe atom in the adsorbed Fe-Pc molecule dominantly involves the Fe 3d(z)2 orbital. These results fully specify the magnetic structure of the system and the process responsible for magnetic transitions. The dynamics of the magnetic transitions induced by tunneling electrons is treated in a strong-coupling approach. The Fe-Pc treatment is extended to the Co-Pc case. The present calculations accurately reproduce the strength of the magnetic transitions as observed by magnetic inelastic electron tunneling spectroscopy experiments; in particular, the dominance of the inelastic current in the conduction of the adsorbed M-Pc molecule is accounted for.
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Gloaguen, E., de Courcy, B., Piquemal, J. - P., Pilme, J., Parisel, O., Pollet, R., Biswal, H. S., Piuzzi, F., Tardivel, B., Broquier, M., & Mons, M. (2010). Gas-Phase Folding of a Two-Residue Model Peptide Chain: On the Importance of an Interplay between Experiment and Theory. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 132(34), 11860–11863.
Résumé: In order to assess the ability of theory to describe properly the dispersive interactions that are ubiquitous in peptide and protein systems, an isolated short peptide chain has been studied using both gas-phase laser spectroscopy and quantum chemistry. The experimentally observed coexistence of an extended form and a folded form in the supersonic expansion was found to result from comparable Gibbs free energies for the two species under the high-temperature conditions (<= 320 K) resulting from the laser desorption technique used to vaporize the molecules. These data have been compared to results obtained using a series of quantum chemistry methods, including DFT, DFT-D, and post-Hartree-Fock methods, which give rise to a wide range of relative stabilities predicted for these two forms. The experimental observation was best reproduced by an empirically dispersion-corrected functional (B97-D) and a hybrid functional with a significant Hartree-Fock exchange term (M06-2X). In contrast, the popular post-Hartree-Fock method MP2, which is often used for benchmarking these systems, had to be discarded because of a very large basis-set superposition error. The applicability of the atomic counterpoise correction (ACP) is also discussed. This work also introduces the mandatory theoretical examination of experimental abundances. Delta H(0 K) predictions are clearly not sufficient for discussion of folding, as the conformation inversion temperature is crucial to the conformation determination and requires taking into account thermodynamical corrections (Delta G) in order to computationally isolate the most stable conformation.
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Grum-Grzhimailo, A. N., Cubaynes, D., Heinecke, E., Hoffmann, P., Zimmermann, P., & Meyer, M. (2010). Generalized geometrical model for photoionization of polarized atoms: II. Magnetic dichroism in the 3p photoemission from the K 3p(6)4s S-2(1/2) ground state. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 43(20), 201002.
Résumé: The generalized geometrical model for photoionization from polarized atoms is extended to include mixing of configurations in the initial atomic and/or the final photoion states. The theoretical results for angle-resolved linear and circular magnetic dichroism are in good agreement with new high-resolution photoelectron data for 3p(-1) photoionization of potassium atoms polarized in the K 3p(6)4s S-2(1/2) ground state by laser optical pumping.
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Guelluy, P. - H., Fontaine-Aupart, M. - P., Grammenos, A., Lecart, S., Piette, J., & Hoebeke, M. (2010). Optimizing photodynamic therapy by liposomal formulation of the photosensitizer pyropheophorbide-a methyl ester: In vitro and ex vivo comparative biophysical investigations in a colon carcinoma cell line. PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, 9(9), 1252–1260.
Résumé: Photodynamic therapy (PDT), induced by a photosensitizer (PS) encapsulated in a nanostructure, has emerged as an appropriate treatment to cure a multitude of oncological and non-oncological diseases. Pyropheophorbide-a methyl ester (PPME) is a second-generation PS tested in PDT, and is a potential candidate for future clinical applications. The present study, carried out in a human colon carcinoma cell line (HCT-116), evaluates the improvement resulting from a liposomal formulation of PPME versus free-PPME. Absorption and fluorescence spectroscopies, fluorescence lifetime measurements, subcellular imaging and co-localization analysis have been performed in order to analyze the properties of PPME for each delivery mode. The benefit of drug encapsulation in DMPC-liposomes is clear from our experiments, with a 5-fold higher intracellular drug delivery than that observed with free-PPME at similar concentrations. The reactive oxygen species (ROSs) produced after PPME-mediated photosensitization have been identified and quantified by using electron spin resonance spectroscopy. Our results demonstrate that PPME-PDT-mediated ROSs are composed of singlet oxygen and a hydroxyl radical. The small amounts of PPME inside mitochondria, as revealed by fluorescence co-localization analysis, could maybe explain the very low apoptotic cell death measured in HCT-116 cells.
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Guilbaud, O., Tissandier, F., Goddet, J. - P., Ribiere, M., Sebban, S., Gautier, J., Joyeux, D., Ros, D., Cassou, K., Kazamias, S., Klisnick, A., Habib, J., Zeitoun, P., Benredjem, D., Mocek, T., Nedjl, J., de Rossi, S., Maynard, G., Cros, B., Boudaa, A., & Calisti, A. (2010). Fourier-limited seeded soft x-ray laser pulse. OPTICS LETTERS, 35(9), 1326–1328.
Résumé: We present what we believe to be the first measurement of the spectral properties of a soft x-ray laser seeded by a high-order harmonic beam. Using an interferometric method, the spectral profile of a seeded Ni-like krypton soft x-ray laser (32.8 nm) generated by optical field ionization has been experimentally determined, and the shortest possible pulse duration has been deduced. The source exhibits a Voigt spectral profile with an FWHM of 3.1+/-0.3 m angstrom, leading to a Fourier-transform pulse duration of 4.7 ps. This value is comparable with the upper limit of the soft x-ray pulse duration determined by experimentally investigating the gain dynamics, from which we conclude that the source has reached the Fourier limit. The measured bandwidth is in good agreement with the predictions of a radiative transfer code, including gain line narrowing and saturation rebroadening. (C) 2010 Optical Society of America
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Ha-Thi, M. - H., Shafizadeh, N., Poisson, L., & Soep, B. (2010). First observation in the gas phase of the ultrafast electronic relaxation pathways of the S-2 states of heme and hemin. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12(45), 14985–14993.
Résumé: The time evolution of electronically excited heme (iron II protoporphyrin IX, [Fe-II PP]) and its associated salt hemin (iron III protoporphyrin IX chloride, [Fe-III PP-Cl]), has been investigated for the first time in the gas phase by femtosecond pump-probe spectroscopy. The porphyrins were excited at 400 nm in the S-2 state (Soret band) and their relaxation dynamics was probed by multiphoton ionization at 800 nm. This time evolution was compared with that of the excited state of zinc protoporphyrin IX [Zn PP] whose S2 excited state likely decays to the long lived S-1 state through a conical intersection, in less than 100 fs. Instead, for [Fe-II PP] and [Fe-III PP-Cl], the key relaxation step from S-2 is interpreted as an ultrafast charge transfer from the porphyrin excited orbital pi* to a vacant d orbital on the iron atom (ligand to metal charge transfer, LMCT). This intermediate LMCT state then relaxes to the ground state within 250 fs. Through this work a new, serendipitous, preparation step was found for Fe II porphyrins, in the gas phase.
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Hamoudi, H., Prato, M., Dablemont, C., Cavalleri, O., Canepa, M., & Esaulov, V. A. (2010). Self-Assembly of 1,4-Benzenedimethanethiol Self-Assembled Monolayers on Gold. LANGMUIR, 26(10), 7242–7247.
Résumé: A study of the self-assembly of 1,4-benzenedimethanethiol (BDMT; HS-CH(2)-(C(6)H(4))-CH(2)-SH) monolayers on gold is presented. Self-assembled monolayers (SAM) are characterized by reflection absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SF) measurements. The ensemble of measurements consistently shows that well-organized BDMT SAMs, with “standing-up” molecules, can be obtained on high quality gold films with incubation in n-hexane provided that N(2)-degassed solutions are used and all preparation steps are performed at 60 degrees C in the absence of ambient light. SE data indicate that the optical interface properties of the BDMT-Au system are different from those of simple alkanethiol SAMs. A possible mechanism for the formation of the “standing-up” phase from the lying-down phase via a hydrogen exchange reaction involving chemisorbed lying-clown and free dithiol molecules is discussed.
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Hartmann, J. - M., Boulet, C., Tran, H., & Nguyen, M. T. (2010). Molecular dynamics simulations for CO2 absorption spectra. I. Line broadening and the far wing of the nu(3) infrared band. JOURNAL OF CHEMICAL PHYSICS, 133(14), 144313.
Résumé: Classical molecular dynamics simulations (CMDS) have been carried out for gaseous CO2 starting from the intermolecular potential energy surface. Through calculations for a large number of molecules treated as rigid rotors, various autocorrelation functions (ACFs) are obtained together with probabilities of rotational changes. Those used in the present paper are the ACFs of the center of mass velocity and of the molecular orientation, and the conditional probability of a change of the angular speed. They enable calculations, respectively, of the mass diffusion coefficient, of the infrared (dipolar) band shape including the wings, and of individual line-broadening coefficients. It is shown that these calculations, free of any adjustable parameter, lead to good agreement with measured values. This is expected from previous studies for the mass diffusion coefficient and line-broadening coefficients, but it is, to our knowledge, the first demonstration of the interest of CMDS for the prediction of band wings. The present results thus open promising perspectives for the theoretical treatment of the difficult problem of far wings profiles. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489349]
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Ivanovskaya, V. V., Zobelli, A., Teillet-Billy, D., Rougeau, N., Sidis, V., & Briddon, P. R. (2010). Enhanced H-2 catalytic formation on specific topological defects in interstellar graphenic dust grain models. PHYSICAL REVIEW B, 82(24), 245407.
Résumé: First-principles models of the formation of H-2 on interstellar media carbonaceous grains are usually concerned with processes occurring on ideal graphenic surfaces. Until now these models are unable to explain the formation of molecular hydrogen due to the presence of absorption barriers that cannot be overcome at the low temperatures of the interstellar media. We propose an approach emphasizing the role of specific topological defects for molecular hydrogen catalysis at interstellar dust grain models. Using the nudged elastic band method combined with density-functional techniques, we obtain the full catalytic cycle for the formation of the H-2 molecule on complex carbon topologies involving the presence of pentagonal rings and C adatoms. Depending on structures, reaction paths can be barrierless or have adsorption barriers as low as 10(-3)-10(-2) eV, which might be easily overcome at the temperatures of the interstellar medium. Such low adsorption barriers indicate that specific carbon grains topological defects are preferential sites for the molecular hydrogen formation in the interstellar medium.
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Ivanovskaya, V. V., Zobelli, A., Teillet-Billy, D., Rougeau, N., Sidis, V., & Briddon, P. R. (2010). Hydrogen adsorption on graphene: a first principles study. EUROPEAN PHYSICAL JOURNAL B, 76(3), 481–486.
Résumé: We present a systematic ab initio study of atomic hydrogen adsorption on graphene. The characteristics of the adsorption process are discussed in relation with the hydrogenation coverage. For systems with high coverage, the resultant strain due to substrate relaxation strongly affects H atom chemisorption. This leads to local structural changes that have not been pointed out to date, namely localized surface curvature. We demonstrate that the hydrogen chemisorption energy barrier is independent of the optimization technique and system size, being associated with the relaxation and rehybridization of the sole adsorbent carbon atom. On the other hand, the H desorption barrier is very sensitive to a correct structural relaxation and is also dependent on the degree of system hydrogenation.
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Jacquemart, D., Gomez, L., Lacome, N., Mandin, J. Y., Pirali, O., & Roy, P. (2010). Measurement of absolute line intensities in the nu(5)-nu(4) band of (C2H2)-C-12 using SOLEIL synchrotron far infrared AILES beamline. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 111(9), 1223–1233.
Résumé: Absolute intensities of about 120 lines of the (C2H2)-C-12 molecule are reported for the nu(4)-nu(5) band between 65 and 192 cm(-1), with an average accuracy of 5%. Vibrational transition dipole moment squared values and empirical Herman-Wallis coefficients are obtained allowing modelling the rotational dependence of the transition dipole moment squared. Special care is taken to accurately determine an apparatus function for the Bruker IFS 125-HR coupled to the synchrotron SOLEIL far infrared AILES beamline in order to minimize its effects on the line parameter retrieval. (C) 2010 Elsevier Ltd. All rights reserved.
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Jaouadi, A., Gaaloul, N., Viaris de Lesegno, B., Telmini, M., Pruvost, L., & Charron, E. (2010). Bose-Einstein condensation in dark power-law laser traps. PHYSICAL REVIEW A, 82, 023613.
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Jiang, J., Abramavicius, D., Falvo, C., Bulheller, B. M., Hirst, J. D., & Mukamel, S. (2010). Simulation of Two-Dimensional Ultraviolet Spectroscopy of Amyloid Fibrils. JOURNAL OF PHYSICAL CHEMISTRY B, 114(37), 12150–12156.
Résumé: Revealing the structure and aggregation mechanism of amyloid fibrils is essential for the treatment of over 20 diseases related to protein misfolding. Coherent two-dimensional (2D) infrared spectroscopy is a novel tool that provides a wealth of new insight into the structure and dynamics of biomolecular systems. Recently developed ultrafast laser sources are extending multidimensional spectroscopy into the ultraviolet (UV) region, and this opens up new opportunities for probing fibrils. In a simulation study, we show that 2DUV spectra of the backbone of a 32-residue beta-amyloid (A beta(9-40)) fibril associated with Alzheimer's disease and two intermediate prefibrillar structures carry characteristic signatures of fibril size and geometry that could be used to monitor its formation kinetics. The dependence of these signals on the fibril size and geometry is explored. We demonstrate that the dominant features of the beta-amyloid fibril spectra are determined by intrainolecular interactions within a single A beta(9-40), and intermolecular interactions at the “external interface” have clear signatures in the fine details of these signals.
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Kara, A., Vizzini, S., Leandri, C., Ealet, B., Oughaddou, H., Aufray, B., & Lelay, G. (2010). Silicon nano-ribbons on Ag(110): a computational investigation. JOURNAL OF PHYSICS-CONDENSED MATTER, 22(4), 045004.
Résumé: We report results of a computational investigation, based on density functional theory, of silicon self-assembled nano-ribbons (Si NRs) on Ag(110). These NRs present a honeycomb-like structure arched on the substrate and forming a closed-packed structure. The calculated STM images match the experimental ones, hinting to a possible new Si structure, mediated by the Ag substrate. The observed new electronic states near the Fermi level were reproduced by the calculations and attributed to a confinement/hybridization tandem.
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Kobayashi, K., Usami, N., Porcel, E., Lacombe, S., & Le Sech, C. (2010). Enhancement of radiation effect by heavy elements. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH, 704(1-3), 123–131.
Résumé: The enhancement of radiobiological effects by heavy elements is reviewed. As an underlying mechanism, Auger effects have been stressed which can be induced via inner-shell photoabsorption or via excitation and/or ionization by secondary electrons. Latter channel of Auger induction expands the applicability of Auger enhancing phenomena to electron and hadron therapy. After discussion on the required characteristics for radiosensitizers, possibility of nanoparticles of Au or Pt is mentioned since they could be synthesized or modified as ideal radiosensitizers. (C) 2010 Elsevier B.V. All rights reserved.
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Lacombe, S., Sabatier, L., Wien, F., & Gauduel, Y. A. (2010). Spatio-temporal radiation biology: new insights and biomedical perspectives. CELL DEATH & DISEASE, 1.
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Laffon, C., Lasne, J., Bournel, F., Schulte, K., Lacombe, S., & Parent, P. (2010). Photochemistry of carbon monoxide and methanol in water and nitric acid hydrate ices: A NEXAFS study. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12(36), 10865–10870.
Résumé: Soft X-ray induced chemistry of H(2)O, CO and CH(3)OH and the effects of the water and nitric acid hydrate (HNO(3)center dot 1.65H(2)O) matrix on the photochemistry of CO and CH(3)OH have been investigated using NEXAFS spectroscopy. For pure H(2)O, CO and CH(3)OH ices, we show that the destruction rates are strongly limited by back reactions, leading to strikingly high survival rates of these molecules upon the harsh irradiation conditions to which they are submitted. We also evidence the interplay between the photochemical reactions of CO and CH(3)OH and those of the matrix. The OH and O radicals released by the photolysis of H(2)O and HNO(3) react with the CO and CH(3)OH and their fragments, considerably reducing the survival rates compared to pure CO and pure CH(3)OH ices, especially in presence of nitric acid, and dramatically enhancing the formation of CO(2) at the expense of CO. Because NEXAFS spectroscopy allows identifying which reactions are important among those possible, it emerges a simple picture of the photochemical routes of CO and CH(3)OH in the H(2)O and HNO(3)/H(2)O environments.
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Lahmam-Bennani, A., Casagrande, E. M. S., Naja, A., Dal Cappello, C., & Bolognesi, P. (2010). Predominance of the second-order, two-step mechanism in the electron impact double ionization of helium at intermediate impact energy. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 43(10), 105201.
Résumé: The (e,3-1e) four-fold differential cross sections (4DCS) are measured for the double ionization of helium in coplanar asymmetric geometry for a wide range of ejected electron energies and at an incident energy of about 600 eV. The experimental angular distributions of the 4DCS are characterized by large angular shifts of the forward and backward lobes with respect to the momentum transfer direction or its opposite, respectively. This validates our previously published results (Lahmam-Bennani et al 2002 J. Phys. B: At. Mol. Opt. Phys. 35 L59) which were questioned by Gotz et al (2003 J. Phys. B: At. Mol. Opt. Phys. 36 L77). A qualitative, kinematical analysis is given which allows relating these shifts and the observed structures in the intensity distributions to the second-order, 'two-step 2' double ionization mechanism, which is shown to predominate over the first-order 'shake-off' and 'two-step 1' mechanisms under the present kinematics.
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Lalmi, B., Oughaddou, H., Enriquez, H., Kara, A., Vizzini, S., Ealet, B., & Aufray, B. (2010). Epitaxial growth of a silicene sheet. APPLIED PHYSICS LETTERS, 97(22), 223109.
Résumé: Using atomic resolved scanning tunneling microscopy, we present here the experimental evidence of a silicene sheet (graphenelike structure) epitaxially grown on a close-packed silver surface [Ag(111)]. This has been achieved via direct condensation of a silicon atomic flux onto the single-crystal substrate in ultrahigh vacuum conditions. A highly ordered silicon structure, arranged within a honeycomb lattice, is synthesized and present two silicon sublattices occupying positions at different heights (0.02 nm) indicating possible sp(2)-sp(3) hybridizations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3524215]
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Lefebvre, R., & Atabek, O. (2010). Exceptional points in multichannel resonance quantization. The European Physical Journal D, 56, 317.
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Matar, E., Bergeron, H., Dulieu, F., Chaabouni, H., Accolla, M., & Lemaire, J. L. (2010). Gas temperature dependent sticking of hydrogen on cold amorphous water ice surfaces of interstellar interest. JOURNAL OF CHEMICAL PHYSICS, 133(10), 104507.
Résumé: Using the King and Wells method, we present experimental data on the dependence of the sticking of molecular hydrogen and deuterium on the beam temperature onto nonporous amorphous solid water ice surfaces of interstellar interest. A statistical model that explains the isotopic effect and the beam temperature behavior of our data is proposed. This model gives an understanding of the discrepancy between all known experimental results on the sticking of molecular hydrogen. Moreover, it is able to fit the theoretical results of Buch et al. [Astrophys. J. 379, 647 (1991)] on atomic hydrogen and deuterium. For astrophysical applications, an analytical formula for the sticking coefficients of H, D, H(2), D(2), and HD in the case of a gas phase at thermal equilibrium is also provided at the end of the article. (C) 2010 American Institute of Physics. [doi:10.1063/1.3484867]
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Meyer, M., Cubaynes, D., Dardis, J., Hayden, P., Hough, P., Richardson, V., Kennedy, E. T., Costello, J. T., Duesterer, S., Li, W. B., Radcliffe, P., Redlin, H., Feldhaus, J., Strakhova, S. I., Gryzlova, E. V., Grum-Grzhimailo, A. N., Taieb, R., & Maquete, A. (2010). Two-color experiments in the gas phase at FLASH. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 181(2-3), 111–115.
Résumé: Intense ultra-short XUV-pulses from the Free Electron Laser in Hamburg (FLASH) were used in combination with the synchronized near-infrared (NIR) radiation from a femtosecond laser to perform two-color experiments on rare gas atoms and small molecules. Results of atomic photoionization in the presence of a NIR dressing field are presented and discussed for the low field regime, i.e. for intensities of less than 10(11) W/cm(2). In particular, the analysis of two-color Above Threshold Ionization (ATI) as a function of the relative orientation of the polarization vectors of both photon beams provided detailed information about the partial photoionization crosssections by comparing the experimental results with theoretical values obtained by employing second-order perturbation theory and the “soft-photon” approximation. Furthermore, a first time-resolved study was performed on the photodissociation of molecular hydrogen. In this proof-of-principle experiment, the excited atomic fragments, produced in the primary interaction with the intense XUV pulse, are probed by a time delayed NIR laser pulse that ionizes these fragments. (C) 2010 Elsevier B.V. All rights reserved.
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Meyer, M., Cubaynes, D., Richardson, V., Costello, J. T., Radcliffe, P., Li, W. B., Duesterer, S., Fritzsche, S., Mihelic, A., Papamihail, K. G., & Lambropoulos, P. (2010). Two-Photon Excitation and Relaxation of the 3d-4d Resonance in Atomic Kr. PHYSICAL REVIEW LETTERS, 104(21), 213001.
Résumé: Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes.
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Mitsuda, H., Miyazaki, M., Nielsen, I. B., Carcabal, P., Dedonder, C., Jouvet, C., Ishiuchi, S., & Fujii, M. (2010). Evidence for Catechol Ring- Induced Conformational Restriction in Neurotransmitters. J. Phys. Chem. Lett., 1(7), 1130–1133.
Résumé: In the neurotransmission process, a specific neurotransmitter binds to a specific receptor in a “key and lock” recognition process. Neurotransmitters, such as the catecholamines, are flexible molecules that can change their shape easily in principle. However, conformations of both the “key” and “lock” must be quite limited to achieve high selectivity. We have investigated the conformational diversity of catecholamines and related molecules by laser spectroscopy. Molecules of the tyrosine family, which contain a phenolic aromatic chromophore, exist as several conformers. In contrast, a single conformer is observed in dopa and other catecholamines, which contain two hydroxyl groups on the benzene moiety (catechol). This demonstrates that the presence of a catechol ring restricts significantly the number of stable conformations.
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Morisset, S., Ferro, Y., & Allouche, A. (2010). Study of the sticking of a hydrogen atom on a graphite surface using a mixed classical-quantum dynamics method. JOURNAL OF CHEMICAL PHYSICS, 133(4), 044508.
Résumé: The sticking of one hydrogen atom chemisorbed on the (0001) graphite surface is investigated using a mixed classical-quantum method. The phonon modes of the system in the collinear scattering approach are included in the dynamics calculations. The vibrational degrees of freedom of the surface (phonons) are treated classically, while the H-surface motion is treated using a one-dimensional quantum wave packet propagation method. The sticking probabilities are calculated and the individual contributions of the phonon bands to the collision dynamics are analyzed for surface temperatures of 10, 150, and 300 K and hydrogen kinetic energies ranging from 0.13 to 1.08 eV. An analytical form of the sticking probability as a function of the surface temperature is also proposed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3463001]
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Murray, C., Dozova, N., McCaffrey, J. G., FitzGerald, S., Shafizadeh, N., & Crepin, C. (2010). Infra-red and Raman spectroscopy of free-base and zinc phthalocyanines isolated in matrices. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12(35), 10406–10422.
Résumé: The infrared absorption spectra of matrix-isolated zinc phthalocyanine (ZnPc) and free-base phthalocyanine (H(2)Pc) have been recorded in the region from 400 to 4000 cm(-1) in solid N(2), Ar, Kr and Xe. Raman spectra have been recorded in doped KBr pellets. The isotopomers HDPc and D(2)Pc have been synthesised in an attempt to resolve the conflicting assignments that currently exist in the literature for the N-H bending modes in H2Pc spectra. A complete correlation between the vibrational modes of the three free-base isotopomers and ZnPc has been achieved. Comparison of the IR and Raman spectroscopic results, obtained with isotopic substitution and with predictions from large basis set ab initio calculations, allows identification of the in-plane (IP) and out-of-plane (OP) N-H bending modes. The largest IP isotope shift is observed in the IR at 1046 cm(-1) and at 1026 cm(-1) in Raman spectra while the largest effect in the OP bending modes is at 764 cm(-1). OP bending modes are too weak to be observed in the experimental Raman data. The antisymmetric N-H stretching mode is observed at similar to 3310 cm(-1) in low temperature solids slightly blue shifted from, but entirely consistent with the literature KBr data. With the exception of the N-H stretches, the recorded H/D isotope shifts in all the N-H vibrations are complex, with the IP bending modes exhibiting small nu H/nu D ratios (the largest value is 1.089) while one of the observed OP modes has a ratio < 1. DFT results reveal that the small ratios arise in particular from strong coupling of the N-H IP bending modes with IP stretching modes of C-N bonds. The unexpected finding of a nu H/nu D ratio smaller than one was analysed theoretically by examining the evolution of the frequencies of the free base by increasing the mass from H to D in a continuous manner. A consequence of this frequency increase in the heavier isotopomer is that the direction of the N-D OP bend is reversed from the N-H OP bend.
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Nave, S., & Jackson, B. (2010). Vibrational mode-selective chemistry: Methane dissociation on Ni(100). PHYSICAL REVIEW B, 81(23), 233408.
Résumé: A first-principles full-dimensional model for CH(4) dissociation on Ni(100) is derived using a reaction path formulation. Vibrational excitation of the methane is found to significantly enhance reactivity when the molecule undergoes transitions to the ground or lower-energy vibrational states with the excess energy converted into motion along the reaction path. The nu(1) vibration has the largest efficacy for promoting reaction, with the nu(3) efficacy smaller, but significant.
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Nave, S., Tiwari, A. K., & Jackson, B. (2010). Methane dissociation and adsorption on Ni(111), Pt(111), Ni(100), Pt(100), and Pt(110)-(1x2): Energetic study. JOURNAL OF CHEMICAL PHYSICS, 132(5).
Résumé: We use density functional theory to examine 24 transition states for methane dissociation on five different metal surfaces. In our calculations, the nonlocal exchange-correlation effects are treated within the generalized gradient approximation using the Perdew-Burke-Ernzerhof functional. In all cases, the minimum energy path for dissociation is over a top site. The barriers are large, 0.66-1.12 eV, and relatively insensitive to the rotational orientation of the (nonreacting) methyl group and the azimuthal orientation of the reactive C-H bond. There is a strong preference on the Pt surfaces for the methyl fragment to bond on the top site, while on the Ni surfaces there is a preference for the hollow or bridge sites. Thus, during the dissociation on Pt, only the low mass H atom needs to significantly move or tunnel, while on Ni, both the dissociating H and the methyl fragment move away from the top site. For all 24 configurations there is a strong force at the transition state to pucker the metal atom over which the reaction occurs. The resulting magnitude of the variation in the barrier height with the motion of this atom varies a bit from surface-to-surface, but is of the order of 1 eV/angstrom. We derive a model for the effective reaction barrier height that includes the effects of lattice motion and substrate temperature and compare with recent experiments and other theoretical studies. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3297885]
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Nimmrich, M., Kittelmann, M., Rahe, P., Mayne, A. J., Dujardin, G., von Schmidsfeld, A., Reichling, M., Harneit, W., & Kuhnle, A. (2010). Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2x1) diamond surfaces using noncontact AFM. Phys. Rev. B, 81(20), 201403.
Résumé: High-purity, type IIa diamond is investigated by noncontact atomic force microscopy (NC-AFM). We present atomic-resolution images of both the electrically conducting hydrogen-terminated C(100)-(2 x 1) : H surface and the insulating C(100)-(2 x 1) surface. For the hydrogen-terminated surface, a nearly square unit cell is imaged. In contrast to previous scanning tunneling microscopy experiments, NC-AFM imaging allows both hydrogen atoms within the unit cell to be resolved individually, indicating a symmetric dimer alignment. Upon removing the surface hydrogen, the diamond sample becomes insulating. We present atomic-resolution images, revealing individual C-C dimers. Our results provide real-space experimental evidence for a (2 x 1) dimer reconstruction of the truly insulating C(100) surface.
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Novaes, F. D., Lorente, N., & Gauyacq, J. - P. (2010). Quenching of magnetic excitations in single adsorbates at surfaces: Mn on CuN/Cu(100). Phys. Rev. B, 82(15), 155401.
Résumé: The lifetimes of spin excitations of Mn adsorbates on CuN/Cu(100) are computed from first principles. The theory is based on a strong-coupling approach that evaluates the decay of a spin excitation due to electron-hole pair creation. Using a previously developed theory [Phys. Rev. Lett. 103, 176601 (2009) and Phys. Rev. B 81, 165423 (2010)], we compute the excitation rates by a tunneling current for all the Mn spin states. A rate equation approach permits us to simulate the experimental results by Loth and co-workers (Nat. Phys. 6, 340 (2010)] for large tunneling currents, taking into account the finite population of excited states. Our simulations give us insight into the spin dynamics, in particular, in the way polarized electrons can reveal the existence of an excited-state population. In addition, it reveals that the excitation process occurs in a way very different from the deexcitation one. Indeed, while excitation by tunneling electrons proceeds via the s and p electrons of the adsorbate, deexcitation mainly involves the d electrons.
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Perez-Gonzalez, O., Zabala, N., Borisov, A. G., Halas, N. J., Nordlander, P., & Aizpurua, J. (2010). Optical Spectroscopy of Conductive Junctions in Plasmonic Cavities. Nano Lett., 10(8), 3090–3095.
Résumé: The optical properties of a nanoparticle dimer bridged by a conductive junction depend strongly on the junction conductivity. As the conductivity increases, the bonding dimer plasmon blueshifts and broadens. For large conductance, a low energy charge transfer plasmon also appears in the spectra with a line width that decreases with increasing conductance. A simple physical model for the understanding of the spectral feature is presented. Our finding of a strong influence of junction conductivity on the optical spectrum suggests that plasmonic cavities might serve as probes of molecular conductance at elevated frequencies not accessible through electrical measurements.
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Perot, M., Lucas, B., Barat, M., Fayeton, J. A., & Jouvet, C. (2010). Mechanisms of UV Photodissociation of Small Protonated Peptides. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3147–3156.
Résumé: Photofragmentation of protonated dipeptides by 263 nm photons is Investigated with,ill experimental technique based oil the detection in coincidence of the ionic and neutral fragments. With this method, it is possible to determine whether the fragmentation takes, place in one or several steps The timing of these steps call also be evaluated The interpretation of the various fragmentation pathways is tentatively developed along the same line IS that previously proposed for tryptophan The fragmentation call be explained by two types of mechanisms internal conversions and direct fragmentations triggered by the migration of the photoactive electron oil positive charged sties or oil oxygen sites
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Perot, M., Lucas, B., Barat, M., Fayeton, J. A., & Jouvet, C. (2010). Mechanisms of UV photodissociation of small protonated peptides. J Phys Chem A, 114(9), 3147–3156.
Résumé: Photofragmentation of protonated dipeptides by 263 nm photons is investigated with an experimental technique based on the detection in coincidence of the ionic and neutral fragments. With this method, it is possible to determine whether the fragmentation takes place in one or several steps. The timing of these steps can also be evaluated. The interpretation of the various fragmentation pathways is tentatively developed along the same line as that previously proposed for tryptophan. The fragmentation can be explained by two types of mechanisms: internal conversions and direct fragmentations triggered by the migration of the photoactive electron on positive charged sites or on oxygen sites.
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Pino, G. A., Oldani, A. N., Marceca, E., Fujii, M., Ishiuchi, S. - I., Miyazaki, M., Broquier, M., Dedonder, C., & Jouvet, C. (2010). Excited state hydrogen transfer dynamics in substituted phenols and their complexes with ammonia: pi pi*-pi sigma* energy gap propensity and ortho-substitution effect. JOURNAL OF CHEMICAL PHYSICS, 133(12), 124313.
Résumé: Lifetimes of the first electronic excited state (S(1)) of fluorine and methyl (o-, m-, and p-) substituted phenols and their complexes with one ammonia molecule have been measured for the 00 transition and for the intermolecular stretching sigma(1) levels in complexes using picosecond pump-probe spectroscopy. Excitation energies to the S(1) (pi pi*) and S(2) (pi sigma*) states are obtained by quantum chemical calculations at the MP2 and CC2 level using the aug-cc-pVDZ basis set for the ground-state and the S(1) optimized geometries. The observed lifetimes and the energy gaps between the (pi pi*) and (pi sigma*) states show a good correlation, the lifetime being shorter for a smaller energy gap. This propensity suggests that the major dynamics in the excited state concerns an excited state hydrogen detachment or transfer (ESHD/T) promoted directly by a S(1)/S(2) conical intersection, rather than via internal conversion to the ground-state. A specific shortening of lifetime is found in the o- fluorophenol-ammonia complex and explained in terms of the vibronic coupling between the pi pi* and pi sigma* states occurring through the out-of-plane distortion of the C-F bond. (C) 2010 American Institute of Physics. [doi:10.1063/1.3480396]
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Pirali, O., Galue, H. A., Dahl, J. E., Carlson, R. M. K., & Oomens, J. (2010). Infrared spectra and structures of diamantyl and triamantyl carbocations. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY, 297(1-3), 55–62.
Résumé: Gas-phase infrared spectra have been recorded for the diamantyl and triamantyl carbocations by infrared multiple photon dissociation (IRMPD) spectroscopy using the free electron laser FELIX. Chemical ionization of the neutral parent diamondoid molecule in an rf ion trap is accompanied by H-atom loss, forming a stable closed-shell carbocation. Comparing the IRMPD spectra with harmonic DFT calculations permits to determine the structures of the species trapped in our set-up. Comparison of experimental and calculated spectra suggests that H-atom abstraction occurs on a tertiary carbon (CH group) rather than on a secondary carbon (CH(2) group), as also indicated by the calculated relative energies of the various isomers. Combining experimental results and DFT calculations, we compare the spectra of neutral and carbocationic forms of adamantane, diamantane and triamantane. Substantial differences are observed between the IR spectra of neutral and ionic species. In the ions, the 3 μm CH stretching modes become much weaker, while the other mid-IR modes strongly gain in intensity. An intense band centered at 1200 cm(-1) due to a CH/CH(2) bending mode appears to be characteristic of the dehydrogenated cationic species. Finally, the intensities of the low frequency modes (<= 900 cm(-1)) associated with carbon cage deformations appear to be most sensitive to the ionization and dehydrogenation state of the molecules. (C) 2010 Elsevier B.V. All rights reserved.
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Porcel, E., Liehn, S., Remita, H., Usami, N., Kobayashi, K., Furusawa, Y., Le Sech, C., & Lacombe, S. (2010). Platinum nanoparticles: a promising material for future cancer therapy? Nanotechnology, 21(8), 85103.
Résumé: Recently, the use of gold nanoparticles as potential tumor selective radiosensitizers has been proposed as a breakthrough in radiotherapy. Experiments in living cells and in vivo have demonstrated the efficiency of the metal nanoparticles when combined with low energy x-ray radiations (below conventional 1 MeV Linac radiation). Further studies on DNA have been performed in order to better understand the fundamental processes of sensitization and to further improve the method. In this work, we propose a new strategy based on the combination of platinum nanoparticles with irradiation by fast ions effectively used in hadron therapy. It is observed in particular that nanoparticles enhance strongly lethal damage in DNA, with an efficiency factor close to 2 for double strand breaks. In order to disentangle the effect of the nano-design architecture, a comparison with the effects of dispersed metal atoms at the same concentration has been performed. It is thus shown that the sensitization in nanoparticles is enhanced due to auto-amplified electronic cascades inside the nanoparticles, which reinforces the energy deposition in the close vicinity of the metal. Finally, the combination of fast ion radiation (hadron therapy) with platinum nanoparticles should strongly improve cancer therapy protocols.
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Quijada, M., Diez Muino, R., Borisov, A. G., Alonso, J. A., & Echenique, P. M. (2010). Lifetime of electronic excitations in metal nanoparticles. New J. Phys., 12, 053023.
Résumé: Electronic excitations in metal particles with sizes up to a few nanometers are shown to have a one-electron character when a laser pulse is applied off the plasmon resonance. The calculated lifetimes of these excitations are in the femtosecond timescale but their values are substantially different from those in bulk. This deviation can be explained from the large weight of the excitation wave function in the nanoparticle surface region, where dynamic screening is significantly reduced. The well-known quadratic dependence of the lifetime with the excitation energy in bulk breaks down in these finite-size systems.
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R. Lefebvre and N. Moiseyev. (2010). Localization of exceptional points with Padé approximants. J. Phys. B: At. Mol. Opt. Phys., 43, 095401.
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R. Uzdin and R. Lefebvre. (2010). Finding and pinpointing exceptional points in open systems. J. Phys. B: At. Mol. Opt. Phys., 43, 235004.
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Raissi, M., Vizzini, S., Langer, G., Rochdi, N., Oughaddou, H., Coudreau, C., Nitsche, S., D'Avitaya, F. A., Aufray, B., & Lazzari, J. L. (2010). Interfacial solid phase reactions in cobalt/aluminum oxide/silicon(001) system. THIN SOLID FILMS, 518(21), 5992–5994.
Résumé: Auger electron spectroscopy, secondary neutral mass spectrometry and high-resolution transmission electron microscopy were used to assess the chemical, morphological and structural modifications after annealing of cobalt/aluminum oxide/silicon(001) hetero-structure The results show that the aluminum oxide forms a diffusion barrier for temperatures lower than 200 degrees C. Beyond this temperature, cobalt atoms diffuse in the silicon region without apparent modification of the barrier At 340 degrees C, the asymmetric diffusion could be explained by the formation of an AlCoO complex oxide playing the role of a diffusion barrier for Si atoms. (C) 2010 Elsevier B V All rights reserved
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Raseev, G., & Bejan, D. (2010). Multipole surface plasmon resonance of an aluminium surface. Opt. Commun., 283(20), 3976–3984.
Résumé: The surface photoelectric effect and the surface plasmon resonances appear when a p/transverse magnetic polarized laser hits a gas-solid interface. We model this effect in the long wave length (LWL) domain (lambda(vac)>10 nm, (h) over cap omega<124 eV) by combining the Ampere-Maxwell equation, written in classical approximation, with the material equation for the susceptibility. The resulting model, called the vector potential from the electron density (VPED), calculates the susceptibility as a product of the bulk susceptibility and the electron density of the actual system. The bulk susceptibility is a sum of the bound electron scalar susceptibility taken from the experiment and of the conduction electron non-local isotropic susceptibility tensor in a jellium metal (Lindhard, 1954 [1]). The electron density is the square of the wave function solution of the Schrodinger equation. The analysis of observables, the reflectance R and the photoelectron yield Y as well as the induced charge density permits to identify and characterize the multipole surface plasmon resonance of Al(111) appearing at omega(m) similar to 0.8 omega(p), or 11-12 eV. (c) 2010 Elsevier B.V. All rights reserved.
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Richardson, V., Costello, J. T., Cubaynes, D., Dusterer, S., Feldhaus, J., van der Hart, H. W., Juranic, P., Li, W. B., Meyer, M., Richter, M., Sorokin, A. A., & Tiedke, K. (2010). Two-photon inner-shell ionization in the extreme ultraviolet. PHYSICAL REVIEW LETTERS, 105(1), 013001.
Résumé: We have observed the simultaneous inner-shell absorption of two extreme-ultraviolet photons by a Xe atom in an experiment performed at the short-wavelength free electron laser facility FLASH. Photoelectron spectroscopy permitted us to unambiguously identify a feature resulting from the ionization of a single electron of the 4d subshell of Xe by two photons each of energy (931)eV. The feature's intensity has a quadratic dependence on the pulse energy. The results are discussed and interpreted within the framework of recent results of ion spectroscopy experiments of Xe obtained at ultrahigh irradiance in the extreme-ultraviolet regime.
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Riedel, D. (2010). Single molecule manipulation at low temperature and laser scanning tunnelling photo-induced processes analysis through time-resolved studies. JOURNAL OF PHYSICS-CONDENSED MATTER, 22(26), 264009.
Résumé: This paper describes, firstly, the statistical analysis used to determine the processes that occur during the manipulation of a single molecule through electronically induced excitations with a low temperature (5 K) scanning tunnelling microscope (STM). Various molecular operation examples are described and the ability to probe the ensuing molecular manipulation dynamics is discussed within the excitation context. It is, in particular, shown that such studies can reveal reversible manipulation for tuning dynamics through variation of the excitation energy. Secondly, the photo-induced process arising from the irradiation of the STM junction is also studied through feedback loop dynamics analysis, allowing us to distinguish between photo-thermally and photo-electronically induced signals.
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Riedel, D., Delattre, R., Borisov, A. G., & Teperik, T. V. (2010). A Scanning Tunneling Microscope as a Tunable Nanoantenna for Atomic Scale Control of Optical-Field Enhancement. Nano Lett., 10(10), 3857–3862.
Résumé: The high stability of a low temperature (9 K) scanning tunneling microscope junction is used to precisely adjust the enhancement of an external pulsed vacuum ultraviolet (VUV) laser The ensuing VUV optical-field strength is mapped on an hydrogenated Si(100) surface by imprinting locally one-photon atomic scale hydrogen desorption Subsequent to irradiation, topography of the Si(100) H surface at the reacted area revealed a desorption spot with unprecedented atomic precision Our results show that the shapes. positions. and sizes of the desorption spots are correlated to the calculated optical-field structure, offering real control of the optical-held distribution at molecular scale
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Ryan, M., Collier, M., de Pujo, P., Crepin, C., & McCaffrey, J. G. (2010). Investigations of the Optical Spectroscopy of Atomic Sodium Isolated in Solid Argon and Krypton: Experiments and Simulations. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3011–3024.
Résumé: The absorption spectra of thin film samples. formed by (lie codeposition of sodium vapor with the rare gases have long been known to consist of complex structures in the region of the atomic sodium “yellow-doublet” lines The photophysical characteristics of the associated luminescence (excitation/emission) spectra. indicate strong Interaction between the excited P state Na atom and the rare gases (Ar, Kr, and Xe) used as host solids. This system is, reinvestigated with new experimental spectroscopic results and molecular dynamics (MD) calculations The so-called “violet” site in Ar and Kr has been produced by laser excitation of thermally deposited samples The simulation of the “spray-on” deposition of thin Films enables identification of tetravacancy (tv) sites of isolation for ground-state atomic sodium in Ar while in Kr this site is found in addition to single vacancy (sv) occupancy various cubic symmetry sites were taken 11110 account to simulate absorption and emission spectra using acculate Interaction potentials For the Na center dot RG diatomics. The well-known 3-fold splitting in absorption. attributed to the Jahn-Teller effect, was very well reproduced but the simulated spectra for all the sites considered ire located in the low energy region of the experimental bands The evolution of the excited state Na atom is followed revealing the nature and symmetry of the Sites that. are transiently occupied. Consistent with the large Stokes shift observed experimentally, there is an extensive rearrangement. of the lattice In the excited state with respect to the ground state. Combining all the experimental and theoretical information, in assignment of experimental violet, blue, and led absorption features is established involving single vacancy, tetravacancy, and hexavacancy sites, respectively, in Ar and Kr
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Salazar Alarcon, L., Chen, L., Esaulov, V. A., Gayone, J. E., Sanchez, E. A., & Grizzi, O. (2010). Thiol Terminated 1,4-Benzenedimethanethiol Self-Assembled Monolayers on Au(111) and InP(110) from Vapor Phase. JOURNAL OF PHYSICAL CHEMISTRY C, 114(47), 19993–19999.
Résumé: We present results of a clean vacuum evaporative adsorption method of assembly of the conjugated dithiol molecule 1,4-benzenedimethanethiol on the surfaces of gold and indium phosphide. Measurements of direct recoil spectroscopy with time-of-flight analysis show in both cases formation of a self-assembled monolayer (SAM) with S atoms available at the SAM-vacuum interface. Investigation of the adsorption kinetics shows that a lying-down phase is formed at low exposures, which precedes the standing up SAM phase. The standing up SAM formation requires exposures of the order of a mega Langmuir. A study of the SAM stability with temperature shows that the S terminated layer survives up to similar to 370 K, above this temperature a reordering of the layer takes piece where S atoms are no longer available at the vacuum interface. Final desorption occurs around 450 K for Au and around 500K for InP.
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Scuderi, D., Maitre, P., Rondino, F., Le Barbu-Debus, K., Lepere, V., & Zehnacker-Rentien, A. (2010). Chiral Recognition in Cinchona Alkaloid Protonated Dimers: Mass Spectrometry and UV Photodissociation Studies. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3306–3312.
Résumé: Chiral recognition in protonated cinchona alkaloid dimers has been studied in mass spectrometry experiments. The experimental setups involved a modified 7T FT-ICR (Fourier transform-ion cyclotron resonance) mass spectrometer (MS) and a modified Paul ion trap both equipped with an electrospray ionization source (ESI). The Paul ion trap has been coupled to a frequency-doubled dye laser. The fragmentation of protonated dimers made from cinchonidine (Cd) and the two pseudoenantiomers of quinine, namely, quinine (Qn) and quinidine (Qd), has been assessed by means of collision-induced dissociation (CID) as well as UV photodissociation (UVPD). Whereas CID fragmentation of the dimers only leads to the evaporation of the monomers, UVPD results in the additional loss of a neutral radical fragment corresponding to the quinuclidinyl radical. The effect of the excitation wavelength and of complexation with H(2)SO(4) has been studied to cast light on the reaction mechanism. Complexation with H(2)SO(4) modifies the photoreactivity of the dimers; only evaporation of the monomeric fragments, quinine, and cinchonidine is observed. Comparison between the mass spectra of the cinchona alkaloid (CdQnH(+)) or (CdQdH(+)) dimers resulting from the UVPD of (CdQnH(2)SO(4)H(+)) and that of bare (CdQnH(+)) helps propose a fragmentation mechanism, which is thought to involve fast proton transfer from the quinuclidine part of a molecular subunit to the quinoline ring. CID and UV fragmentation experiments show that the homochiral dimer is more strongly bound than the heterochiral adduct.
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Sizun, M., Bachellerie, D., Aguillon, F., & Sidis, V. (2010). Investigation of ZPE and temperature effects on the Eley-Rideal recombination of hydrogen atoms on graphene using a multidimensional graphene-H-H potential. Chem. Phys. Lett., 498(1-3), 32–37.
Résumé: We study the Eley-Rideal recombination of H atoms on graphene under the physical conditions of the interstellar medium. Effects of the ZPE motions of the chemisorbed H atom and of the graphene thermal motions are investigated. Classical molecular dynamics calculations undertaken with the multidimensional potential of Bachellerie et al. [Phys. Chem. Chem. Phys. 11 (2009) 2715] are reported. The ZPE effects are the strongest. The closer the collision energy is to the classical reaction threshold the more sizeable the effects. The quantum reaction cross section is also estimated below and above the classical threshold using a capture model. (C) 2010 Elsevier B.V. All rights reserved.
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Smirnova, I. N., Cuisset, A., Hindle, F., Mouret, G., Bocquet, R., Pirali, O., & Roy, P. (2010). Gas-Phase Synchrotron FTIR Spectroscopy of Weakly Volatile Alkyl Phosphonate and Alkyl Phosphate Compounds: Vibrational and Conformational Analysis in the Terahertz/Far-IR Spectral Domain. JOURNAL OF PHYSICAL CHEMISTRY B, 114(50), 16936–16947.
Résumé: The high brilliance of the AILES beamline at the SOLEIL synchrotron facility has been exploited for the study of the gas-phase vibrational spectra of weakly volatile organophosphorous compounds. The propagation of the synchrotron radiation in long path length gas cells allowed improvements in the sensitivity limits and spectral coverage compared with a previous study, performed by our group with conventional thermal sources.' A ppm level detection in the entire IR domain up to terahertz (THz) frequencies has been realized for dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), triethyl phosphate (TEP), and diethyl (2-methylallyl)phosphonate (DEMaP). In the present study, the assignment of the gas-phase vibrational and the conformational analysis of the two most stable conformers of DMMP and TMP have been extended to the torsional THz spectra in the 20-120 cm(-1) range. The improvement of the SIN ratio below 600 cm(-1) has permitted for the first time a gas-phase conformational analysis of the two weakly volatile and highly flexible TEP and DEMaP compounds. The experimental far-infrared (FIR)/THz spectra have been studied taking into account four low-energy conformers determined by means of high level of theory quantum chemistry calculations. Finally, due to its particularly low vapor pressure, the detection of gas-phase tributyl phosphate (TBP) in the FIR domain was unsuccessful. Nevertheless, the mid-IR/near-IR spectra of TBP recorded in a multipass cell heated to 355 K have been assigned with the harmonic vibrational predictions of the most stable conformer.
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Steeb, F., Mathias, S., Wiesenmayer, M., Fischer, A., Aeschlimann, M., Bauer, M., & Gauyacq, J. P. (2010). Probing adsorbate dynamics with chirped laser pulses in a single-pulse scheme. PHYSICAL REVIEW B, 82(16), 165430.
Résumé: Femtosecond dynamics of the model-like adsorption system Cs/Cu(111) is probed by two-photon photoelectron spectroscopy (2PPE) using phase-modulated (chirped) laser pulses. The experimental data are quantitatively modeled within a wavepacket propagation approach under explicit consideration of the adsorbate motion. The results enable us to assign characteristic chirped-pulse 2PPE features to the ultrafast adsorbate dynamics associated with the excited state lifetime and the adsorbate motion, and to improve on the qualitative interpretation of experimental data as published in Petek et al. [J. Phys. Chem. A 104, 10234 (2000)]. Our results show that nonlinear photoemission with a chirped pulse in a single-pulse scheme can complement real-time studies based on pump-probe schemes to gain quantitative insights into the femtosecond dynamics of ultrafast surface processes.
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Steenkeste, K., Tfibel, F., Perree-Fauvet, M., Briandet, R., & Fontaine-Aupart, M. - P. (2010). Tracking the Photosensitizing Antibacterial Activity of Mono(acridyl)bis(arginyl)porphyrin (MABAP) by Time-Resolved Spectroscopy. JOURNAL OF PHYSICAL CHEMISTRY A, 114(9), 3334–3339.
Résumé: Photodynamic inactivation (PDI) is currently receiving interest for its potential as an antimicrobial treatment. Although photosensitizing agents and light have been used for medical purposes for a very long time, only a little information is available about the mechanism of PDI for bacteria. Pseudomonas aeruginosa is a Gram negative bacteria involved in chronic infections in cystic fibrosis patients and also one of the commonest agents of hospital acquired infections. In the present study the sensitivity of Pseudomonas aeruginosa to the phototoxic effects of the mono(acridyl)bis(arginyl)porphyrin (MABAP) has been investigated as well as the photophysical and photochemical properties of this cationic porphyrin complexed to [poly(dG-dC)](2) to investigate the mechanisms that lead to bacteria inactivation. Both picosecond time-resolved fluorescence and femtosecond to nanosecond transient absorption measurements give evidence that while MABAP can react through its triplet state and/or an ultrafast electron transfer with guanine, its intercalation between GC base pairs is not the main target of MABAP photoactivity. The analysis of both fluorescence emission and excitation spectra reveals the occurrence of an energy transfer through the DNA double helix between the acridine and porphyrin chromophores of MABAP, as previously observed for the stacked free molecule in solution. This efficient process may lead to the excitation of twice more porphyrin chromophores in MABAP by comparison to other cationic porphyrins.
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Teillet-Billy, D., Rougeau, N., Ivanovskaya, V. V., & Sidis, V. (2010). Interaction of Atoms with Graphenic-Type Surfaces for the Chemistry of the Interstellar Medium: New Properties of H Dimers on the Surface. INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 110(12), 2231–2236.
Résumé: Following the works of Rougeau et al. (Chem Phys Lett 2006, 431,135) and Ferro et al. (Phys Rev B 2008, 78, 085417) on the one-sided double chemisorption of H atoms on graphenic platelets, we investigate the two-sided double chemisorption using DFT-GGA PW91 calculations. Equilibrium characteristics and potential energy curves for chemisorption are reported for the ortho, meta, para, and bottom positions. Contrary to the one-sided case, the two-sided ortho chemisorption, as well as the bottom position, is barrier-less, whereas the two-sided para chemisorption exhibits an activation barrier. The highest occupied Kohn-Sham orbital (HOKSO) of the H-graphene radical is shown to signal the privileged barrier-less double chemisorption sites. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2231-2236, 2010
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Tissandier, F., Sebban, S., Ribiere, M., Gautier, J., Zeitoun, P., Lambert, G., Sardinha, A. B., Goddet, J. - P., Burgy, F., Lefrou, T., Valentin, C., Rousse, A., Guilbaud, O., Klisnick, A., Nejdl, J., Mocek, T., & Maynard, G. (2010). Observation of spectral gain narrowing in a high-order harmonic seeded soft-x-ray amplifier. PHYSICAL REVIEW A, 81(6), 063833.
Résumé: We report an observation of spectral gain narrowing of a high-order harmonic amplified by a soft-x-ray optical-field-ionized plasma. The temporal coherence and spectral linewidth of both the seeded and unseeded soft-x-ray lasers were experimentally measured using a varying-path-difference interferometer. The results showed that the high-order harmonic is subject to a strong spectral narrowing during its propagation in the plasma amplifier without rebroadening at saturation. This is in good agreement with a radiative transfer calculation including gain narrowing and saturation rebroadening.
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Tiwari, A. K., Nave, S., & Jackson, B. (2010). The temperature dependence of methane dissociation on Ni(111) and Pt(111): Mixed quantum-classical studies of the lattice response. JOURNAL OF CHEMICAL PHYSICS, 132(13), 134702.
Résumé: The barrier to the dissociative adsorption of methane on metal surfaces is generally large, and its height can vary with the motion of the lattice atoms. One fully quantum and three different mixed quantum-classical approaches are used to examine this reaction on Ni(111) and Pt(111) surfaces, using potential energy surfaces derived from density functional theory. The three approximate methods are benchmarked against the exact quantum studies, and two of them are shown to work reasonably well. The mixed models, which treat the lattice motion classically, are used to examine the lattice response during the reaction. It is found that the thermal motion of the lattice atoms strongly modifies the reactivity, but that their motion is not significantly perturbed. Based on these results, new models for methane reactions are proposed based on a sudden treatment of the lattice motion and shown to agree well with the exact results. In these new models, the reaction probability at different surface temperatures is computed from static surface reaction probabilities, allowing for a quantum calculation of the reaction probability without having to explicitly treat the motion of the heavy lattice atoms.
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Tulej, M., Pino, T., Pachkov, M., & Maier, J. P. (2010). Electronic transitions of the C5H- anion. MOLECULAR PHYSICS, 108(7-9), 865–871.
Résumé: Electronic transitions of the triplet chain C5H- anion were studied using detachment spectroscopy. The system detected in the vicinity of the electron detachment threshold is assigned to the b(3)A <- a(3) A transition with a dipole bound state (DBS) character. The second system measured by autodetachment spectroscopy is attributed to the c(3)A <- a(3)A Feshbach electronic transition. Negative anharmonicity of the vibrational progression built upon the low frequency CCC in-plane bending mode nu(12) is observed in both DBS and Feshbach states. This indicates a barrier to linearity on the potential energy surface in both excited states. The triplet chain C5H- anion exhibits similar electronic properties to C3H-. Renner-Teller and vibronic effects between the (3)A DBS and Feshbach states are inferred and may explain the stabilisation of the DBS. This interaction is weaker in C5H- than C3H- leading to smaller barrier heights on the potential energy surface.
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Turowski, M., Crepin, C., Gronowski, M., Guillemin, J. - C., Coupeaud, A., Couturier-Tamburelli, I., Pietri, N., & Kolos, R. (2010). Electronic absorption and phosphorescence of cyanodiacetylene. JOURNAL OF CHEMICAL PHYSICS, 133(7).
Résumé: Electronic absorption and emission spectra have been investigated for cyanodiacetylene, HC(5)N, an astrophysically relevant molecule. The analysis of gas-phase absorption was assisted with the parallel rare gas matrix isolation experiments and with density functional theory (DFT) predictions concerning the excited electronic states. Mid-UV systems (B) over tilde (1)Delta <-(X) over tilde (1)Sigma(+) (origin at 282.5 nm) and (A) over tilde (1)Sigma(-)<-(X) over tilde (1)Sigma(+) (306.8 nm) were observed. Vibronic assignments have been facilitated by the discovery of the visible phosphorescence a (a) over bar (3)Sigma(+) <- (X) over tilde (1)Sigma(+) in solid Ar, Kr, and Xe. Phosphorescence excitation spectra, as well as UV absorption measurements in rare gas matrices, revealed the enhancement of (A) over tilde <- (X) over tilde transitions. The vibronic structure of dispersed phosphorescence spectra supplied new data concerning the ground state bending fundamentals of matrix-isolated HC(5)N. The experimental singlet-triplet splitting, 2.92 eV in Ar, closely matches the value of 3.0 eV predicted by DFT. (C) 2010 American Institute of Physics. [doi:10.1063/1.3472978]
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Usami, N., Kobayashi, K., Hirayama, R., Furusawa, Y., Porcel, E., Lacombe, S., & Le Sech, C. (2010). Comparison of DNA Breaks at Entrance Channel and Bragg Peak Induced by Fast C6+ Ions-Influence of the Addition of Platinum Atoms on DNA. JOURNAL OF RADIATION RESEARCH, 51(1), 21–26.
Résumé: When energetic carbon ion beam (GeV range) goes through the matter, inelastic processes such as electronic ionization, molecular and nuclear fragmentation occur. For carbontherapy (hadrontherapy) purpose, it is of interest to compare the number of DNA breaks -single SSB or double DSB- for a given dose at the entrance channel and at the Bragg peak to look for a possible differential effect in the number of DNA breaks induced at these two locations. Samples of free plasmids DNA and complexes of plasmids DNA added with molecules containing platinum have been placed at different locations of an experimental setup simulating penetration depths of the ion beam in water and irradiated by carbon ions 290 MeV/amu. The DNA breaks have been quantified by subsequent electrophoresis on agarose gels. To disentangle the respective role of the direct and indirect effect, a free radical scavenger of hydroxyl radicals HO degrees -dimethyl sulfoxide DMSO- has been added in some of the experiments. In the range of Linear Energy Transfert -LET 13 – 110 keV/mu m-, the number of the DSB was found to be constant versus the LET for a given dose. Contrary, the number of the SSB decreases at the Bragg peak compared to the entrance channel. In the presence of platinum, the number of single and double breaks was considerably enhanced, and follows a similar behaviour than in the free-DNA experiments. Quantitative results on DNA damages do not show significant enhancement due to the nuclear or to the molecular fragmentation in the present experiments.
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Waharte, F., Steenkeste, K., Briandet, R., & Fontaine-Aupart, M. - P. (2010). Diffusion Measurements inside Biofilms by Image-Based Fluorescence Recovery after Photobleaching (FRAP) Analysis with a Commercial Confocal Laser Scanning Microscope. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 76(17), 5860–5869.
Résumé: Research about the reactional and structural dynamics of biofilms at the molecular level has made great strides, owing to efficient fluorescence imaging methods in terms of spatial resolution and fast acquisition time but also to noninvasive conditions of observation consistent with in situ biofilm studies. In addition to conventional fluorescence intensity imaging, the fluorescence recovery after photobleaching (FRAP) module can now be routinely implemented on commercial confocal laser scanning microscopes (CLSMs). This method allows measuring of local diffusion coefficients in biofilms and could become an alternative to fluorescence correlation spectroscopy (FCS). We present here an image-based FRAP protocol to improve the accuracy of FRAP measurements inside “live” biofilms and the corresponding analysis. An original kymogram representation allows control of the absence of perturbing bacterial movement during image acquisition. FRAP data analysis takes into account molecular diffusion during the bleach phase and uses the image information to extract molecular diffusion coefficients. The fluorescence spatial intensity profile analysis used here for the first time with biofilms is supported both by our own mathematical model and by a previously published one. This approach was validated to FRAP experiments on fluorescent-dextran diffusion inside Lactoccocus lactis and Stenotrophomonas maltophilia biofilms, and the results were compared to previously published FCS measurements.
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Yang, H., Mayne, A. J., Boucherit, M., Comtet, G., Dujardin, G., & Kuk, Y. (2010). Quantum Interference Channeling at Graphene Edges. Nano Lett., 10(3), 943–947.
Résumé: Electron scattering at graphene edges is expected to make a crucial contribution to the electron transport in graphene nanodevices by producing quantum interferences. Atomic-scale scanning tunneling microscopy (STM) topographies of different edge structures of monolayer graphene show that the localization of the electronic density of states along the C-C bonds, a property unique to monolayer graphene, results in quantum interference patterns along the graphene carbon bond network, whose shapes depend only on the edge structure and not on the electron energy.
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Yu, S. S., Pearson, J. C., Drouin, B. J., Sung, K., Pirali, O., Vervloet, M., Martin-Drumel, M. A., Endres, C. P., Shiraishi, T., Kobayashi, K., & Matsushima, F. (2010). Submillimeter-wave and far-infrared spectroscopy of high-J transitions of the ground and nu(2)=1 states of ammonia. JOURNAL OF CHEMICAL PHYSICS, 133(17), 174317.
Résumé: Complete and reliable knowledge of the ammonia spectrum is needed to enable the analysis and interpretation of astrophysical and planetary observations. Ammonia has been observed in the interstellar medium up to J = 18 and more highly excited transitions are expected to appear in hot exoplanets and brown dwarfs. As a result, there is considerable interest in observing and assigning the high J (rovibrational) spectrum. In this work, numerous spectroscopic techniques were employed to study its high J transitions in the ground and nu(2) = 1 states. Measurements were carried out using a frequency multiplied submillimeter spectrometer at Jet Propulsion Laboratory (JPL), a tunable far-infrared spectrometer at University of Toyama, and a high-resolution Bruker IFS 125 Fourier transform spectrometer (FTS) at Synchrotron SOLEIL. Highly excited ammonia was created with a radiofrequency discharge and a dc discharge, which allowed assignments of transitions with J up to 35. One hundred and seventy seven ground state and nu(2) = 1 inversion transitions were observed with microwave accuracy in the 0.3-4.7 THz region. Of these, 125 were observed for the first time, including 26 Delta K = 3 transitions. Over 2000 far-infrared transitions were assigned to the ground state and nu(2) = 1 inversion bands as well as the nu(2) fundamental band. Of these, 1912 were assigned using the FTS data for the first time, including 222 Delta K = 3 transitions. The accuracy of these measurements has been estimated to be 0.0003-0.0006 cm(-1). A reduced root mean square error of 0.9 was obtained for a global fit of the ground and nu(2) = 1 states, which includes the lines assigned in this work and all previously available microwave, terahertz, far-infrared, and mid-infrared data. The new measurements and predictions reported here will support the analyses of astronomical observations by high-resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA. The comprehensive experimental rovibrational energy levels reported here will permit further refinement of the potential energy surface to improve ammonia ab initio calculations and facilitate assignment of new high-resolution spectra of hot ammonia. (C) 2010 American Institute of Physics. [doi:10.1063/1.3499911]
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Actes de Conférences |
Alessi, D., Berrill, M., Wang, Y., Domingue, S. R., Martz, D., Luther, B. M., Meng, L., Guilbaud, O., Klisnick, A., & Rocca, J. J. (2010). Beam Characteristics of an Injection-Seeded Solid-Target Plasma Soft X-Ray Laser. In 2010 23RD ANNUAL MEETING OF THE IEEE PHOTONICS SOCIETY (pp. 341–342). IEEE.
Résumé: We have measured the near-field and far-field profiles (for lambda=13.9 nm) as well as temporal coherence (for lambda=18.9 nm) of injection-seeded and self-seeded solid-target amplifiers. The measurements were compared with model simulations.
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Basire, M., Parneix, P., Calvo, F., Pino, T., & Bréchignac, P. (2010). Simulation of the IR absorption spectrum of the naphthalene molecule. In Proceeding of the international symposium on PAHs and the Universe (Vol. Ed Ch. Joblin and A.G.M. Tielens, Juin 2010).
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Bernhardt, B., Ozawa, A., Jacquet, P., Jacquey, M., Kobayashi, Y., Udem, T., Holzwarth, R., Guelachvili, G., Haensch, T. W., & Picque, N. (2010). Trace gas detection with frequency comb Fourier transform spectroscopy. In 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS).
Résumé: Dual-comb Fourier transform spectroscopy with cavity enhancement holds much promise for trace gas sensing. Broadband high resolution spectra of ammonia around 1.0 μm are recorded within 18 μs and a noise-equivalent-absorption of 1 10(-10) cm(-1) Hz(-1/2). (C) 2010 Optical Society of America
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Bernhardt, B., Sorokin, E., Jacquet, P., Thon, R., Becker, T., Sorokina, I. T., Haensch, T. W., & Picque, N. (2010). 2.4 μm Dual-Comb Spectroscopy. In 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS).
Résumé: A proof-of-principle experiment of mid-infrared frequency comb Fourier transform spectroscopy is carried out with two interfering Cr2+:ZnSe femtosecond oscillators, emitting around 2400 nm. Spectra of acetylene are measured within 10 μs with 12 GHz resolution. (C)2010 Optical Society of America
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Brubach, J. B., Manceron, L., Rouzieres, M., Pirali, O., Balcon, D., Tchana, F. K., Boudon, V., Tudorie, M., Huet, T., Cuisset, A., & Roy, P. (2010). Performance of the AILES THz-Infrared beamline at SOLEIL for High resolution spectroscopy. In WIRMS 2009: 5TH INTERNATIONAL WORKSHOP ON INFRARED MICROSCOPY AND SPECTROSCOPY WITH ACCELERATOR BASED SOURCES (Vol. 1214, pp. 81–84).
Résumé: The new THz beamline (AILES) located at the third generation Synchrotron Radiation source SOLEIL., is now operating for applications in a wide variety of research themes. In particular, this source with its adapted optics allows high resolution spectroscopic measurements of molecules in the entire infrared and THz range. This presentation focuses on the performances concerning flux, spectral range and stability for molecular spectroscopy. Thanks to these performances, the coupling of synchrotron radiation from a highly stable third generation source with high resolution FTIR spectrometer and with a long path cell (150 m or more) can be particularly advantageous. This fact is related to the optics of the beamline permitting the entire source to be used without aperture stop (entrance iris), even for measurements at highest-resolution of similar to 0.1 μeV (10(-3) cm(-1)).
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Crepin C., S. N., Chin W., Galaup J.P., M. C. J. G., & Arabei S.M. (2010). Absorption, fluorescence et émission stimulée de AlCl-Phtalocyanine en matrice d’Argon. In PROCEEDINGS of the International Conférence on “ Bases moléculaires, membranaires et cellulaires du fonctionnement des biosystèmes“ (157).
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Cuisset, A., Smirnova, I., Bocquet, R., Hindle, F., Mouret, G., Yang, C., Pirali, O., & Roy, P. (2010). Gas phase THz spectroscopy of toxic agent simulant compounds using the AILES synchrotron beamline. In WIRMS 2009: 5TH INTERNATIONAL WORKSHOP ON INFRARED MICROSCOPY AND SPECTROSCOPY WITH ACCELERATOR BASED SOURCES (Vol. 1214, pp. 85–87).
Résumé: A new study is currently underway aiming at recording and assigning the gas phase rovibrational spectra of several organophosphorus and organosulphur compounds in the THz frequency domain. Thanks to the exceptional properties of flux, brilliance and spectral range of the AILES beamline coupled to the FTIR spectrometer, the gas phase vibrational spectra of low volatility organophosphorous compounds have been recorded across the entire THz frequency range. High resolution FTIR spectroscopy was used to record the pure rotational and the low-frequency rovibrational spectrum of DMSO. A comparison between the spectra measured with the AILES beamline and the spectra obtained with optoelectronic THz sources is possible.
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Delahaye, J., Gresillon, S., Leveque-Fort, S., Sojic, N., & Fort, E. (2010). Fluorescence Correlation Spectroscopy on Nano-fakir Surfaces. In SINGLE MOLECULE SPECTROSCOPY AND IMAGING III (Vol. 7571).
Résumé: Single biomolecule behaviour can reveal crucial information about processes not accessible by ensemble measurements. It thus represents a real biotechnological challenge. Common optical microscopy approaches require pico- to nano-molar concentrations in order to isolate an individual molecule in the observation volume. However, biologically relevant conditions often involve micromolar concentrations, which impose a drastic reduction of the conventional observation volume by at least three orders of magnitude. This confinement is also crucial for mapping sub-wavelength heterogeneities in cells, which play an important role in many biological processes. We propose an original approach, which couples Fluorescence Correlation Spectroscopy (FCS), a powerful tool to retrieve essential information on single molecular behaviour, and nano-fakir substrates with strong field enhancements and confinements at their surface. These electromagnetic singularities at nanometer scale, called “hotspots”, are the result of the unique optical properties of surface plasmons. They provide an elegant means for studying single-molecule dynamics at high concentrations by reducing dramatically the excitation volume and enhancing the fluorophore signal by several orders of magnitude. The nano-fakir substrates used are obtained from etching optical fiber bundles followed by sputtering of a gold thin-film. It allows one to design reproducible arrays of nanotips.
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Gans, B., Boye-Peronne, S., Douin, S., & Gauyacq, D. (2010). TOWARDS A QUANTITATIVE STUDY OF THE VUV PHOTOLYSIS OF METHANE: PRELIMINARY EXPERIMENT ON TRICHLOROMETHANE. In PHYSICS AND ASTROPHYSICS OF PLANETARY SYSTEMS (Vol. 41, pp. 455–458).
Résumé: Photolysis of methane in Titan's stratosphere is the starting point of gas phase carbon chemistry. Quantitative studies of methane photolytic products are of utmost importance for Titan atmosphere models. With this aim, two experimental strategies are presented in this article. Preliminary results demonstrate the possibility of using CRDS absorption coupled with pulsed photolysis on the example of a halogenated derivative of methane: Trichloromethane (CHCl(3)).
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Mandon, J., Jacquet, P., Bernhardt, B., Jacquey, M., Guelachvili, G., Haensch, T. W., & Picque, N. (2010). Sensitive and Simple Frequency Comb Fourier Transform Spectrometer with a Multipass Cell. In 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS).
Résumé: Multipass cells offer a simple manner to enhance the sensitivity of dual-comb Fourier transform spectrometer. 1.5 μm spectra spanning 125 nm and exhibiting a noise-equivalent absorption coefficient of 4.10(-9) cm(-1)Hz(-1/2) are recorded within 63 μs. (C)2010 Optical Society of America
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Ros, D., Guilbaud, O., Kazamias, S., Pittmana, M., Lagron, J. - C., Zielbauer, B., Habib, J., Chambaret, J. - P., Mourou, G., Cassou, K., Cros, B., Maynard, G., Zeitoun, P., Sebban, S., Gautier, J., Klisnick, A., de Rossi, S., Jacquemot, S., Audebert, P., Zimmer, S. P. D., & Kuehl, T. (2010). LASERIX : a high-repetition-rate laser facility for performing intense XUV sources for applications. Perspectives for XUV sources in ILE and ELI projects. In LIGHT AT EXTREME INTENSITIES: OPPORTUNITIES AND TECHNOLOGICAL ISSUES OF THE EXTREME LIGHT INFRASTRUCTURE (Vol. 1228, pp. 421–434). AIP Conference Proceedings, 1228.
Résumé: In this paper we present the perspectives of the development of the XUV laser sources using High-power laser facilities. We focus our paper on the present statuts of the LASERIX facility and especially its role in the development of the XUV laser sources considering the French “Institut de la Lumiere Extreme” (I LE) and the potential European project Extreme Light Infrastructure (ELI). Finally, we present one typical experiment performed in that context with the facility. It is dedicated to the fundamental study irradiation induced damage in DNA samples.
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Roy, P., Brubach, B., Manceron, L., Rouzieres, M., Pirali, O., Creff, G., Kwabia-Tchana, F., & Peng, W. (2010). The AILES Beamline for THz and IR spectroscopy. In 35TH INTERNATIONAL CONFERENCE ON INFRARED.
Résumé: The infrared beamline (AILES) at the third generation Synchrotron Radiation source SOLEIL is available for users. This beamline exploits infrared and THz synchrotron radiation from both edge emission and the constant field conventional source. The performances including flux, spatial distribution of the photons, spectral range and stability are discussed and the optical system and spectroscopic stations are described. The combined source with the adapted optics for beam transport offers high flux and brilliance for all kinds of infrared experiments. We will briefly review the main research themes and future developments and illustrate the potential use with two examples.
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Chapitres de Livres |
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K. Le Barbu-Debus. (2010). The role of deformation energy of bi-functional entities on the diastereoisomers formation. In Anne Zehnacker (Ed.), Chiral Recognition in the Gas Phase (pp. 47–59).
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