Peer-reviewed Publications |
Alata, I., Omidyan, R., Dedonder-Lardeux, C., Broquier, M., & Jouvet, C. (2009). Electronically excited states of protonated aromatic molecules: benzaldehyde. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(48), 11479–11486.
Résumé: The photofragmentation spectrum of protonated benzaldehyde has been recorded in the 435-385 nm wavelength range. The first excited state is a pi pi* state, strongly red shifted compared to the pi pi* state of neutral benzaldehyde. The spectrum presents well resolved vibronic bands in contrast to some other protonated aromatic molecules like benzene or tryptophan in which the excited state dynamics is so fast that no vibrational structure can be observed. The bands can be assigned on the basis of a Franck-Condon analysis using ground and excited state frequencies calculated at the CC2/TZVP level.
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Aubry, G., Meance, S., Couraud, L., Haghiri-Gosnet, A. - M., & Kou, Q. (2009). Intracavity microfluidic dye laser droplet absorption. MICROELECTRONIC ENGINEERING, 86(4-6), 1368–1370.
Résumé: An original design for droplet absorption measurement is presented. A microfluidic dye laser is combined with a droplet production system to realise intracavity absorption measurement on few nanoliter volumes. Conditions on droplets for obtaining laser signal are investigated and absorption measurement proof of concept is demonstrated. (C) 2009 Elsevier B.V. All rights reserved.
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Azima, A., Duesterer, S., Radcliffe, P., Redlin, H., Stojanovic, N., Li, W., Schlarb, H., Feldhaus, J., Cubaynes, D., Meyer, M., Dardis, J., Hayden, P., Hough, P., Richardson, V., Kennedy, E. T., & Costello, J. T. (2009). Time-resolved pump-probe experiments beyond the jitter limitations at FLASH. APPLIED PHYSICS LETTERS, 94(14).
Résumé: Using a noninvasive, electro-optically based electron bunch arrival time measurement at FLASH (free electron laser in Hamburg) the temporal resolution of two-color pump-probe experiments has been significantly improved. The system determines the relative arrival time of the extended ultraviolet pulse of FLASH and an amplified Ti:sapphire femtosecond-laser pulse at the interaction region better than 90 fs rms. In a benchmarking pump-probe experiment using two-color above threshold ionization of noble gases, an enhancement in the timing resolution by a factor of 4 compared to the uncorrected data is obtained.
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Bachellerie, D., Sizun, M., Aguillon, F., & Sidis, V. (2009). Effects of a Nonrigid Graphene Surface on the LH Associative Desorption of H Atoms and on the Deexcitation of Nascent H-2 Molecules Colliding with Model Walls of Carbonaceous Porous Material. J. Phys. Chem. A, 113(1), 108–117.
Résumé: A planar slab of 200 C atoms bound by the Brenner potential is used to study the Langmuir-Hinshelwood (LH) recombination of two physisorbed H atoms on a graphene sheet and to simulate afterward successive collisions of the nascent H-2 molecule with pore walls of a carbonaceous dust grain of the interstellar medium. The study is based on successive propagations of classical trajectories for the 200 C + 2 H atoms. The characteristics of H2 molecules formed by the LH reaction on the flexible surface are found to differ but negligibly from those formed on a rigid one. Collisions of those H,, molecules with graphitic pore walls are studied next. Reflection from and “trapping” onto the surface is observed and discussed. The most important energy transfer is from the molecule vibration to its rotation. This conversion mediates the transfer of the molecule internal energy to its translation or to surface heating. It is found that a single H-2-surface impact has little effect on the internal energy of the molecules. The grain absorbs on the average but a very weak energy. Several impacts are required to appreciably cool the molecule. The molecule cooling is accompanied by a significant increase of its translational energy. The swifter the molecules are or get, the larger the number of their impacts on the surface they undergo per unit time and the more efficiently cooled they get.
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Bachellerie, D., Sizun, M., Aguillon, F., Teillet-Billy, D., Rougeau, N., & Sidis, V. (2009). Unrestricted study of the Eley-Rideal formation of H-2 on graphene using a new multidimensional graphene-H-H potential: role of the substrate. Phys. Chem. Chem. Phys., 11(15), 2715–2729.
Résumé: The Brenner potential is adapted to handle chemical interactions and reactions of H atoms at a graphene surface. The adapted potential reproduces several important features of DFT computed data and reveals an extended puckering of the surface upon its adsorption of an H atom. This potential is used to investigate in a much more realistic way than has been done before, the Eley-Rideal abstraction reaction producing H-2 in H + H-graphene collisions at energies E-col <= 0.2 ev. The graphene surface is represented by a slab of 200 carbon atoms and the study is carried out using classical molecular dynamics for vertical incidences in a cylinder centered about the chemisorption axis. A highlight of the present study is that upon the arrival of the gas phase H atom, the adsorbent C atom is attracted and pulls out its surrounding surface atoms. The hillock thus formed remains puckered until the newly formed molecule is released. The range of impact parameters leading to reaction depends on the collision energy and is governed by the shape of the entrance channel potential; the reaction probability in this range is 100%. On average, in the studied E-col range, the available energy (3.92 eV + E-col) is shared as: 69 52% for the internal energy, 11-23% for the translation energy and 20 25% for the energy imparted the surface. Also, the average vibration and rotation energy levels of the nascent H-2 molecule are, respectively, < v > = 5-4 and < i > = 2-4.
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Baffou, G., Mayne, A. J., Comtet, G., Dujardin, G., Stauffer, L., & Sonnet, P. (2009). SiC(0001) 3 x 3 Heterochirality Revealed by Single-Molecule STM Imaging. J. Am. Chem. Soc., 131(9), 3210–3215.
Résumé: We report a description of the SiC(0001) 3 x 3 silicon carbide reconstruction based on single-molecule scanning tunneling microscopy (STM) observations and density functional theory calculations. We show that the SiC(0001) 3 x 3 reconstruction can be described as contiguous domains of right and left chirality distributed at the nanoscale, which breaks the to date supposed translational invariance of the surface. While this surface heterochirality remains invisible in STM topographies of clean surfaces, individual metal-free phthalocyanine molecules chemisorbed on the surface act as molecular lenses to reveal the surface chirality in the STM topographies. This original method exemplifies the ability of STM to probe atomic-scale structures in detail and provides a more complete vision of a frequently studied SiC reconstruction.
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Bagchi, S., Falvo, C., Mukamel, S., & Hochstrasser, R. M. (2009). 2D-IR Experiments and Simulations of the Coupling between Amide-I and Ionizable Side Chains in Proteins: Application to the Villin Headpiece. JOURNAL OF PHYSICAL CHEMISTRY B, 113(32), 11260–11273.
Résumé: The carboxylate side chains of Asp and Glu have significant coupling with the amide states of the backbone of the Villin headpiece. In two-dimensional spectroscopy, cross peaks are observed between these side chains and the main amide-I band. To model the absorption of the side chains, the electric field variations of vibrational frequencies of a carboxylic acid group (neutral form, CH(3)-COOH) and a carboxylate group (ionized form, CH(3)-COO(-)) are parametrized by means of density functional theory calculations. Simulations indicate that the side chains significantly couple to only one or two amide-I modes out of all of the amino acid residues which makes them useful as spectroscopic markers, providing information about the local structural behavior of the protein. Both experiment and simulations show that the cross peaks between the carboxylate and the amide-I bands are significantly diminished above the melting temperature,
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Basire, M., Parneix, P., Calvo, F., Pino, T., & Brechignac, P. (2009). Temperature and Anharmonic Effects on the Infrared Absorption Spectrum from a Quantum Statistical Approach: Application to Naphthalene. JOURNAL OF PHYSICAL CHEMISTRY A, 113(25), 6947–6954.
Résumé: A method is developed to Calculate the finite-temperature infrared absorption spectrum of polyatomic molecules with energy levels described by a second-order Dunham expansion. The anharmonic couplings are fully incorporated in the calculation of the quantum density of states, achieved using a Wang-Landau Monte Carlo procedure, as well as in the determination of transition energies. Additional multicanonical simulations provide the microcanonical absorption intensity as a function of both the absorption wavelength and the internal energy of the molecule. The finite-temperature spectrum is finally obtained by Laplace transformation of this microcanonical histogram. The present scheme is applied to the infrared spectrum of naphthalene, for which we quantity the shifting, broadening, and third-order effects as a continuous function of temperature. The influence of anharmonicity and couplings is manifested on the nontrivial variations of these features with increasing temperature.
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Bellec, A., Ample, F., Riedel, D., Dujardin, G., & Joachim, C. (2009). Imaging Molecular Orbitals by Scanning Tunneling Microscopy on a Passivated Semiconductor. Nano Lett., 9(1), 144–147.
Résumé: Decoupling the electronic properties of a molecule from a substrate is of crucial importance for the development of single-molecule electronics. This is achieved here by adsorbing pentacene molecules at low temperature on a hydrogenated Si(100) surface (12 K). The low temperature (5 K) scanning tunneling microscope (STM) topography of the single pentacene molecule at the energy of the highest occupied molecular orbital (HOMO) tunnel resonance clearly resembles the native HOMO of the free molecule. The negligible electronic coupling between the molecule and the substrate is confirmed by theoretical STM topography and diffusion barrier energy calculations.
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Bellec, A., Riedel, D., Dujardin, G., Boudrioua, O., Chaput, L., Stauffer, L., & Sonnet, P. (2009). Electronic properties of the n-doped hydrogenated silicon (100) surface and dehydrogenated structures at 5 K. PHYSICAL REVIEW B, 80(24), 245434.
Résumé: We present a comparative study of the electronic properties of the clean Si(100) and the hydrogenated Si(100):H surfaces performed with a low-temperature (5 K) scanning tunneling microscope. Various surface structures such as single silicon dangling bonds and bare silicon dimers created by local desorption of hydrogen atoms from the Si(100):H surface are also investigated. The experimental scanning tunneling spectroscopy (STS) curves acquired locally on each of these structures are compared with STS measurements performed on the Si(100) and Si(100):H surfaces. First principle density-functional theory calculations of the projected local density of states, taking into account the influence of the dopant atoms (As), enable to assign the observed STS spectra.
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Beroff, K., Chabot, M., Mezdari, F., Martinet, G., Tuna, T., Desesquelles, P., Le Padellec, A., & Barat, M. (2009). Fragmentation of small carbon clusters, a review. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 267(6), 866–871.
Résumé: An overview of the works devoted to fragmentation of small carbon clusters is given in a first part. Fragmentation of swift neutral and (multi) charged carbon clusters studied with the AGAT spectrometer is presented and discussed in a second part. (C) 2009 Elsevier B.V. All rights reserved.
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Bizau, J. - M., Mosnier, J. - P., Kennedy, E. T., Cubaynes, D., Wuilleumier, F. J., Blancard, C., Champeaux, J. - P., & Folkmann, F. (2009). Photoionization of the Ne-like Si4+ ion in ground and metastable states in the 110-184-eV photon energy range. PHYSICAL REVIEW A, 79(3).
Résumé: We present measurements of the absolute photoionization cross section of the neonlike Si4+ ion over the 110-184 eV photon energy range. The measurements were performed using two independent merged-beam setups at the super-ACO and ASTRID synchrotron-radiation facilities, respectively. Signals produced in the photoionization of the 2p subshell of the Si4+ ion both from the 2p(6) S-1(0) ground state and the 2p(5)3s P-3(0,2) metastable levels were observed. Calculations of the 2p photoionization cross sections were carried out using a multi-configuration Dirac-Fock code. They give results in good agreement with the measured spectra. Comparison with other available theoretical results is also presented.
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Blandin, P., Leveque-Fort, S., Lecart, S., Cossec, J. C., Potier, M. - C., Lenkei, Z., Druon, F., & Georges, P. (2009). Time-gated total internal reflection fluorescence microscopy with a supercontinuum excitation source. APPLIED OPTICS, 48(3), 553–559.
Résumé: We present the instrumental development of a versatile total internal reflection fluorescence lifetime imaging microscopy setup illuminated by a supercontinuum laser source. It enables performing wide-field fluorescence lifetime. imaging with subwavelength axial resolution for a large range of fluorophores. The short overall acquisition time and the axial resolution are well suited for dynamic neurobiological applications. (C) 2009 Optical Society of America
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Bourguignon, B., Zheng, W., Carrez, S., Ouvrard, A., Fournier, F., & Dubost, H. (2009). Deriving the complete molecular conformation of self-assembled alkanethiol molecules from sum-frequency generation vibrational spectra. Phys. Rev. B, 79(12), 125433.
Résumé: The sum frequency generation (SFG) spectrum of CH(2) and CH(3) modes in the self-assembled monolayer of octadecanethiol is modeled in order to understand the reasons of the very low SFG intensity of CH(2) modes and to investigate quantitatively the two types of L-shaped conformations qualitatively suggested in the literature. CH(2) modes are assumed local in order to calculate easily the spectrum of any conformation, and ab initio molecular hyperpolarizabilities are used. It is found that the absence of CH(2) bands does not imply an all-trans conformation and vice versa. Several conformations are compatible with SFG, but only one of them can be arranged on Au(111) and completely agrees with x-ray diffraction. All conformational details of the L-shape molecules are obtained.
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Brunetto, R., Pino, T., Dartois, E., Cao, A. - T., d'Hendecourt, L., Strazzulla, G., & Brechignac, P. (2009). Comparison of the Raman spectra of ion irradiated soot and collected extraterrestrial carbon. ICARUS, 200(1), 323–337.
Résumé: We use a low pressure flame to produce soot by-products as possible analogues of the carbonaceous dust present in diverse astrophysical environments, such as circumstellar shells, diffuse interstellar medium, planetary disks, as well as in our own Solar System. Several soot samples, displaying an initial chemical diversity from aromatic to aliphatic dominated material, are irradiated with 200-400 keV H(+), He(+), and Ar(++) ions, with fluences comprised between 10(14) and 10(16) ions/cm(2), to simulate expected radiation induced modification on extraterrestrial carbon. The evolution of the samples is monitored using Raman spectroscopy, before, during, and after irradiation. A detailed analysis of the first- and second-order Raman spectra is performed, using a fitting combination of Lorentzian and/or Gaussian-shaped bands. Upon irradiation, the samples evolve toward an amorphous carbon phase. The results suggest that the observed variations are more related to vacancy formation than ionization processes. A comparison with Raman spectra of extraterrestrial organic matter and other irradiation experiments of astrophysically relevant carbonaceous materials is presented. The results are consistent with previous experiments showing mostly amorphization of various carbonaceous materials. Irradiated soots have Raman spectra similar to those of some meteorites, IDPs, and Comet Wild 2 grains collected by the Stardust mission. Since the early-Sun expected irradiation fluxes sufficient for amorphization are compatible with accretion timescales, our results support the idea that insoluble organic matter (IOM) observed in primitive meteorites has experienced irradiation-induced amorphization prior to the accretion of the parent bodies, emphasizing the important role played by early solar nebula processing. (C) 2008 Elsevier Inc. All Fights reserved.
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Calvo, F., & Parneix, P. (2009). Phase Space Theory of Evaporation in Neon Clusters: The Role of Quantum Effects. JOURNAL OF PHYSICAL CHEMISTRY A, 113(52), 14352–14363.
Résumé: Unimolecular evaporation of neon clusters containing between 14 and 148 atoms is theoretically investigated in the framework of phase space theory. Quantum effects are incorporated in the vibrational densities of states, which include both zero-point and anharmonic contributions, and in the possible tunneling through the centrifugal barrier. The evaporation rates, kinetic energy released, and product angular momentum are calculated as a function of excess energy or temperature in the parent cluster and compared to the classical results. Quantum fluctuations are found to generally increase both the kinetic energy released and the angular momentum of the product, but the effects on the rate constants depend nontrivially on the excess energy. These results are interpreted as due to the very few vibrational states available in the product cluster when described quantum mechanically. Because delocalization also leads to much narrower thermal energy distributions, the variations of evaporation observables as a function of canonical temperature appear much less marked than in the microcanonical ensemble. While quantum effects tend to smooth the caloric curve in the product cluster, the melting phase change clearly keeps a signature on these observables. The microcanonical temperature extracted from fitting the kinetic energy released distribution using an improved Arrhenius form further Suggests a backbending in the quantum Ne(13) Cluster that is absent in the classical system. Finally, in contrast to delocalization effects, quantum tunneling through the centrifugal barrier does not play any appreciable role on the evaporation kinetics of these rather heavy clusters.
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Calvo, F., Parneix, P., & Basire, M. (2009). Quantum densities of states of fluxional polyatomic systems from a superposition approximation. JOURNAL OF CHEMICAL PHYSICS, 130(15).
Résumé: The superposition method is used to calculate quantum densities of states of polyatomic systems with multiple isomeric structures. For each isomer, anharmonicities are included rigorously using a Dunham expansion of the vibrational energy levels and short exchange Monte Carlo simulations are used to compute the individual quantum densities of states. The method is applied to the computation of thermodynamical properties of the Ar(13) and Ne(13) clusters. The canonical heat capacities are found in very satisfactory agreement with the predictions of quantum or semiclassical sampling methods.
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Canario, A. R., Guillemot, L., Grizzi, O., Bandurin, Y., & Esaulov, V. A. (2009). Scattering of F atoms and anions on a TiO2(110) surface. SURFACE SCIENCE, 603(8), 1099–1105.
Résumé: Results of a study of energy losses and electron transfer processes for grazing scattering of fluorine atoms and anions scattering along different azimuthal orientations of the TiO2 crystal are presented. We observe strong variations in the overall intensity of scattered particles which are due to channelling effects. The energy losses do not show strong variations as a function of crystal azimuth except for the case of scattering along the (001) direction between the bridging oxygen atom rows, where we also observe differences in the energy losses of scattered ions and neutrals. We attribute this to the fact that larger F- survival occurs for trajectories staying farther from the surface, when also the energy losses remain small. The overall characteristics of energy losses are attributed mainly to trajectory effects due to scattering in regions of different electron density. Measurements of the ratio of scattered ions to the total scattered flux, i.e. the ion fractions which reflect electron capture and loss processes, show that these are not the same for incident anions and atoms. A strong difference for scattering along the (001) direction is observed, where at low incident energies a strong survival of incident ions occurs. These results are tentatively discussed in terms of non resonant electron capture at lattice O- sites and electron loss into the conduction band or by collisional detachment with bridging O atoms. (C) 2009 Elsevier B.V. All rights reserved.
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Carrera, A., Nielsen, I. B., Carcabal, P., Dedonder, C., Broquier, M., Jouvet, C., Domcke, W., & Sobolewski, A. L. (2009). Biradicalic excited states of zwitterionic phenol-ammonia clusters. J. Chem. Phys., 130(2), 024302.
Résumé: Phenol-ammonia clusters with more than five ammonia molecules are proton transferred species in the ground state. In the present work, the excited states of these zwitterionic clusters have been studied experimentally with two-color pump probe methods on the nanosecond time scale and by ab initio electronic-structure calculations. The experiments reveal the existence of a long-lived excited electronic state with a lifetime in the 50-100 ns range, much longer than the excited state lifetime of bare phenol and small clusters of phenol with ammonia. The ab initio calculations indicate that this long-lived excited state corresponds to a biradicalic system, consisting of a phenoxy radical that is hydrogen bonded to a hydrogenated ammonia cluster. The biradical is formed from the locally excited state of the phenolate anion via an electron transfer process, which neutralizes the charge separation of the ground state zwitterion.
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Chakraborty, S., Omidyan, R., Alata, I., Nielsen, I. B., Dedonder, C., Broquier, M., & Jouvet, C. (2009). Protonated Benzene Dimer: An Experimental and Ab Initio Study. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131(31), 11091–11097.
Résumé: The excitation spectrum of the protonated benzene dimer has been recorded in the 415-600 nm wavelength range. In contrast to the neutral iso-electronic benzene dimer, its absorption spectrum extends in the visible spectral region. This huge spectral shift has been interpreted with ab initio calculations, which indicate that the first excited states should be charge transfer states.
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Chiaravalloti, F., Riedel, D., Dujardin, G., Pinto, H. P., & Foster, A. S. (2009). STM topography and manipulation of single Au atoms on Si(100). Phys. Rev. B, 79(24), 245431.
Résumé: The low-temperature (12 K) adsorption of single Au atoms on Si(100) is studied by scanning tunneling microscopy (STM). Comparison between experimental and calculated STM topographies as well as density-functional-theory calculations of the adsorption energies enable us to identify two adsorption configurations of Au atoms between Si-dimer rows (BDRs) and on top of Si-dimer rows (TDRs). In both adsorption configurations, the Au atoms are covalently bound to two Si atoms through a partial electron transfer from Si to Au. STM manipulation confirms that the TDR adsorption configuration is metastable, whereas the BDR one is the most stable configuration.
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Cranney, M., Chalopin, Y., Mayne, A. J., & Dujardin, G. (2009). Adsorption and organisation of para-hexaphenyl molecules on Si(100). Appl. Phys. A, 94(4), 767–773.
Résumé: Para-hexaphenyl molecules (p-6P: C(36)H(26)) can be grown as nanofibres on various surfaces having optical properties of technological relevance. We report here the first observations of the initial stages of adsorption of individual p-6P molecules on Si(100)-(2x1) using room temperature Scanning Tunnelling Microscopy (STM). Depending on the substrate temperature, the hexaphenyl molecules adsorb in two configurations; indicating both weak and strong chemisorption. All six phenyl rings are clearly visible and the molecules are found to adsorb with characteristic angles between the long axis of the molecule and the silicon dimer rows. A statistical analysis of the spatial distribution of the molecules suggests that the clustering required for crystallographic nanofibre growth does not occur at the atomic scale under the experimental conditions used here.
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Cubaynes, D., Guilbaud, S., Wuilleumier, F. J., Meyer, M., Heinecke, E., Riek, K., Zimmermann, P., Yalcinkaya, M., Fritzsche, S., Strakhova, S. I., & Grum-Grzhimailo, A. N. (2009). Photoionization from the 2p subshell of the laser-excited aligned Na*2p(6)3p P-2(3/2) state. PHYSICAL REVIEW A, 80(2).
Résumé: High resolution angle-resolved photoelectron spectra from Na atoms laser excited and aligned in the Na* 2p(6)3p P-2(3/2) state are investigated experimentally and theoretically in the region of the Na+ 2p(5)3p manifold. A prominent influence of the alignment on the relative line intensities is observed. The measured linear alignment dichroism is in good agreement with the theoretical results obtained in the multiconfigurational Dirac-Fock approximation as well as in a generalized geometrical model, which is extended to the description of angular distributions of photoelectrons from polarized atoms.
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Diaz-Tendero, S., Borisov, A. G., & Gauyacq, J. - P. (2009). Extraordinary electron propagation length in a metallic double chain supported on a metal surface. Phys. Rev. Lett., 102(16), 166807.
Résumé: The present theoretical study shows that a double chain of Cu metal atoms adsorbed on a Cu(111) metal surface can guide an excited electron for distances exceeding 10 nm. The nanostructure appears to be quasi-decoupled from the substrate and thus to act as a nanowire. The origin of the above phenomenon is the interference between the decay of the quasistationary 1D sp-band states localized on each chain. This allows to approach the situation of the formation of bound states in the continuum first discussed in quantum systems by von Neumann and Wigner.
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Diaz-Tendero, S., Olsson, F. E., Borisov, A. G., & Gauyacq, J. - P. (2009). Excited electron dynamics in Cu nanowires supported on a Cu(111) surface. Phys. Rev. B, 79(11), 115438.
Résumé: We present a theoretical study of the excited electron dynamics in infinite Cu monoatomic chains (nanowires) supported on a Cu(111) surface. A joint approach based on the wave packet propagation and the density functional theory is used. The nanowire-induced potential obtained from ab initio density functional theory calculations serves as an input for the wave-packet propagation study of the excited electron dynamics. The energy dispersion and the lifetime of an unoccupied one-dimensional (1D) nanowire-localized electronic band with sp character are obtained. From the group velocity and lifetime of the 1D sp-band states, it follows that an excited electron can travel about four to five atomic sites along the nanowire before its escape into the bulk. We show that the surface projected band gap and the surface Brillouin zone backfolding of the substrate states play a fundamental role in the lifetime of the nanowire-localized states.
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Dowek, D., Haouas, A., Guillemin, R., Elkharrat, C., Houver, J. - C., Li, W. B., Catoire, F., Journel, L., Simon, M., & Lucchese, R. R. (2009). Recoil frame photoemission in inner-shell photoionization of small polyatomic molecules. EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, 169, 85–93.
Résumé: Going from a diatomic to a polyatomic linear or non-linear molecule, the description of molecular frame photoemission in photoionization of molecules involves a function of increasing complexity. Using the electron-ion Vector Correlation method, which provides the emission velocity vectors of the emitted charged particles in a dissociative photoionization reaction, generally gives access to Recoil Frame Photoelectron Angular Distributions (RFPADs). We report results for site selected inner-shell photoionization of the N(2)O molecule induced by elliptically polarized light, where the primary ionization reaction leads to the production of several fragmentation channels. Ion fragment kinetic energy release distributions as well as RFPADs are reported for selected two ion-channels containing the complete parent molecule. Experimental results are compared with recent multi-channel Schwinger configuration interaction (MCSCI) ab initio calculations at the level of the RFPADs. The link with the original computed molecular frame photoelectron angular distributions (MFPADs) is discussed.
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Dowek, D., Picard, Y. J., Billaud, P., Elkharrat, C., & Houver, J. C. (2009). Molecular Frame Photoemission: Probe of the Photoionization Dynamics for Molecules in the Gas Phase. CHINESE JOURNAL OF CHEMICAL PHYSICS, 22(2), 178–186.
Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. This paper reports a comparative study of non-resonant and resonant photoionization of D(2) induced by VUV circularly polarized synchrotron radiation at SOLEIL at the level of the molecular frame photoelectron angular distributions (MFPADs). We use the vector correlation method which combines imaging and time-of-flight resolved electron-ion coincidence techniques, and a generalized formalism for the expression of the I(chi, theta(e), phi(e)) MFPADs, where chi is the orientation of the molecular axis with respect to the light quantization axis and (theta(e), phi(e)) the electron emission direction in the molecular frame. Selected MFPADs for a molecule aligned parallel or perpendicular to linearly polarized light, or perpendicular to the propagation axis of circularly polarized light, are presented for dissociative photoionization (DPI) of D(2) at two photon excitation energies, hv=19 eV, where direct PI is the only channel opened, and hv=32.5 eV, i.e. in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. We discuss in particular the properties of the circular dichroism characterizing photoemission in the molecular frame for direct and resonant PI. In the latter case, a remarkable behavior is observed which may be attributed to the interference occurring between undistinguishable autoionization decay channels.
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El Hassan, N., Bizau, J. M., Blancard, C., Cosse, P., Cubaynes, D., Faussurier, G., & Folkmann, F. (2009). Photoionization cross sections of iron isonuclear sequence ions: Fe2+ to Fe6+. PHYSICAL REVIEW A, 79(3).
Résumé: We have measured the absolute photoionization cross sections of Fe2+ to Fe6+ ions in the photon energy range covering the first ionization threshold up to 160 eV. Particular interest is emphasized on the region of the 3p -> 3d excitations. The experimental data are compared to the results of calculations we have performed using a spectral opacity code, as well as to available R-matrix and one-electron calculations. It is shown that often the theoretical results tend to overestimate the intensity of the 3p -> 3d photoexcitations. An anomalously low value of the integrated oscillator strength is measured for Fe2+ ion.
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Eschwege, P., Deniset-Besseau, A., Ferlicot, S., Lecart, S., Leveque-Fort, S., Lwaleed, B. A., Benoit, G., Droupy, S., Hubert, J., & Fontaine-Aupart, M. P. (2009). DETECTION OF HUMAN BLADDER CANCER CELL RESISTANCE TO MVAC CHEMOTHERAPY BY FLUORESCENCE IMAGING. EUROPEAN UROLOGY SUPPLEMENTS, 8(4), 152.
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Falvo, C., Palmieri, B., & Mukamel, S. (2009). Coherent infrared multidimensional spectra of the OH stretching band in liquid water simulated by direct nonlinear exciton propagation. JOURNAL OF CHEMICAL PHYSICS, 130(18), 184501.
Résumé: The two-dimensional vibrational response of the disordered strongly fluctuating OH exciton band in liquid water is investigated using a new simulation protocol. The direct nonlinear exciton propagation generalizes the nonlinear exciton equations to include nonadiabatic time dependent Hamiltonian and transition dipole fluctuations. The excitonic picture is retained and the large cancellation between Liouville pathways is built-in from the outset. The sensitivity of the photon echo and double-quantum-coherence techniques to frequency fluctuations, molecular reorientation, intermolecular coupling, and the two-exciton coherence is investigated. The photon echo is particularly sensitive to the frequency fluctuations and molecular reorientation, whereas the double-quantum coherence provides a unique probe for intermolecular couplings and two-exciton coherence.
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Feagin, J. M., Colgan, J., Huetz, A., & Reddish, T. J. (2009). Electron-Pair Excitations and the Molecular Coulomb Continuum. PHYSICAL REVIEW LETTERS, 103(3), 033002.
Résumé: Electron-pair excitations in the molecular hydrogen continuum are described by quantizing rotations of the momentum plane of the electron pair about the pair's relative momentum. A heliumlike description of the molecular photodouble ionization is thus extended to higher angular momenta of the electron pair. A simple three-state superposition is found to account surprisingly well for recent observations of noncoplanar electron-pair, molecular-axis angular distributions.
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Fillion, J. H., Amiaud, L., Congiu, E., Dulieu, F., Momeni, A., & Lemaire, J. L. (2009). D-2 desorption kinetics on amorphous solid water: from compact to porous ice films. Phys. Chem. Chem. Phys., 11(21), 4396–4402.
Résumé: The desorption kinetics of D-2 from amorphous solid water (ASW) films have been studied by the temperature-programmed desorption (TPD) technique in the 10-30 K temperature range. Compact (and nonporous) films were grown at 120 K over a copper substrate. Ultra-thin porous films were additionally grown at 10 K over the compact base. The TPD spectra from compact and from up to 20 monolayers (ML) porous films were compared. The simulation of the TPD experimental traces provides the corresponding D-2 binding-energy distributions. As compared to the compact case, the binding-energy distribution found for the 10 ML porous film clearly extends to higher energies. To study the transition from compact to porous ice, porous films of intermediate thicknesses (<10 ML), including ultra-thin films (<1 ML), were grown over the compact substrate. The thermal D-2 desorption peak was found to shift to higher temperatures as the porous ice network was progressively formed. This behavior can be explained by the formation of more energetic binding sites related to porous films. TPD spectra were also modelled by using a combination of the two energy distributions, one associated to a bare compact ice and the other associated to a 10 ML porous ice film. This analysis reveals a very fast evolution of the binding-energy distribution towards that of porous ice. Our results show that few ML of additional porous film are sufficient to produce a sample for which the D-2 adsorption can be described by the energy distribution found for the 10 ML porous film. These experiments then provide evidence that the binding energy of D-2 on ASW ice is primarily governed by the topological and morphological disorder of the surface at molecular scale.
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Flores, M., O'Rourke, B. E., Yamazaki, Y., & Esaulov, V. A. (2009). Potential and kinetic sputtering of alkanethiol self-assembled monolayers by impact of highly charged ions. PHYSICAL REVIEW A, 79(2).
Résumé: Highly charged ions have been used to study the sputtering of positive molecular fragments from mercaptoundecanoic acid and dodecanethiol self-assembled monolayers on gold surfaces. The samples were bombarded with Arq+ (4 <= q <= 10) ions with kinetic energies from 2 to 18 keV. The main fragments detected were H+, CnH2n+, and Cn+1O2H2n+1+ from mercaptoundecanoic and H+, CnH2n+, and Cn+1H2n+3+ from dodecanethiol. The proton yields were increased with larger charge state q of the highly charged ion (HCI) in both samples, scaling as q(gamma), with gamma similar to 5. The charge state dependence is discussed in terms of electron transfer to the HCI. The final yield of protons depends on molecular functional group characteristics, orientation on the surface, and reneutralization phenomena.
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Gaaloul, N., Jaouadi, A., Pruvost, L., Telmini, M., & Charron, E. (2009). Controlled deflection of cold atomic clouds and of Bose-Einstein condensates. EUROPEAN PHYSICAL JOURNAL D, 53, 343.
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Gauyacq, J. P., Diaz-Tendero, S., & Borisov, A. G. (2009). Mapping of the electron transmission through the wall of a quantum corral. Surf. Sci., 603(13), 2074–2081.
Résumé: We report on a theoretical study of the escape of confined surface states electrons from quantum corrals made of Cu adatoms on a Cu(1 1 1) surface. This study maps electron transmission through the corral wall and provides an extension of our earlier work focused on confinement in Cu corrals [S. Diaz-Tendero, F.E. Olsson, A.G. Borisov, J.P. Gauyacq, Phys. Rev. B 77 (2008) 205403]. The existence of two decay modes for the confined surface state is stressed: (i) non-resonant tunnelling through the corral wall concentrated on the Cu adatoms and (ii) a resonant-induced decay involving the transient formation of a resonant state localized on top of the corral wall. The present mapping of the electron transmission reveals how the interference between the two decay modes works: there exist regions where the electron leaves the corral, balanced by regions where it enters the corral, though the global behaviour of the quasi-stationary states is electron escape from the corral. (C) 2009 Elsevier B.V. All rights reserved.
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Grégoire, G., Lucas, B., Barat, M., Fayeton, J. A., Dedonder-Lardeux, C., & Jouvet, C. (2009). UV photoinduced dynamics in protonated aromatic amino acid. Eur. Phys. J. D, 51(1), 109–116.
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Grum-Grzhimailo, A. N., Gryzlova, E. V., Cubaynes, D., Heinecke, E., Yalcinkaya, M., Zimmermann, P., & Meyer, M. (2009). The generalized geometrical model for the photoionization of polarized atoms: application to linear dichroism in the 2p photoemission from Na 3(2)S and Na*3(2)P initial states. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(17).
Résumé: The generalized geometrical model utilized for the interpretation of photoelectron spectra is extended to the photoionization from polarized atoms. Within this model, the linear magnetic and the linear alignment dichroisms in the photoemission are calculated. The theoretical results are compared to those obtained from high-resolution angle-resolved photoelectron spectra, which were recorded upon 2p(-1) photoionization of sodium atoms oriented in the Na 2p(6)3s S-2(1/2) ground and Na* 2p(6)3p P-2(1/2) laser-excited states or aligned in the Na* 2p(6)3p P-2(3/2) state. Good overall agreement is found between theory and experiment.
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Guillemot, L., & Bobrov, K. (2009). Chirality induced by surface strain studied using scanning tunneling microscopy. PHYSICAL REVIEW B, 79(20), 201406.
Résumé: We present a scanning tunneling microscopy study of a thermally annealed oxygen covered Cu(110)-(2x1)-O surface. The thermal annealing results in step bunching followed by formation of strained terraces. The mechanical strain causes local compression of the Cu lattice accompanied with reflection symmetry breaking as measured by comparative analysis of the atomically resolved topographies. On the strained terraces the oblique Cu lattice favors oxygen rearrangement into a chiral adsorption phase. Chiral surface organization is evidenced by formation of enantiomorphic domains on the strained terraces.
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Kadhane, U., Pérot, M., Lucas, B., Barat, M., Fayeton, J. A., Jouvet, C., Ehlerding, A., Kirketerp, M. - B. S., Nielsen, S. B., Wyer, J. A., & Zettergren, H. (2009). Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations. Chemical Physics Letters, 480(1-3), 57–61.
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Kara, A., Leandri, C., Davila, M., Padova, P., Ealet, B., Oughaddou, H., Aufray, B., & Lay, G. (2009). Physics of Silicene Stripes. JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 22(3), 259–263.
Résumé: Silicene, a monolayer of silicon atoms tightly packed into a two-dimensional honeycomb lattice, is the challenging hypothetical reflection in the silicon realm of graphene, a one-atom thick graphite sheet, presently the hottest material in condensed matter physics. If existing, it would also reveal a cornucopia of new physics and potential applications. Here, we reveal the epitaxial growth of silicene stripes self-aligned in a massively parallel array on the anisotropic silver (110) surface. This crucial step in the silicene “gold rush” could give a new kick to silicon on the electronics road-map and open the most promising route towards wide-ranging applications. A hint of superconductivity in these silicene stripes poses intriguing questions related to the delicate interplay between paired correlated fermions, massless Dirac fermions and bosonic quasiparticles in low dimensions.
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Kelkensberg, F., Lefebvre, C., Siu, W., Ghafur, O., Nguyen-Dang, T. T., Atabek, O., Keller, A., Serov, V., Johnsson, P., Swoboda, M., Remetter, T., L’Huillier, A., Zherebtsov, S., Sansone, G., Benedetti, E., Ferrari, F., Nisoli, M., Lépine, F., Kling, M. F., & Vrakking, M. J. J. (2009). Molecular Dissociative Ionization and Wave-Packet Dynamics Studied Using Two-Color XUV and IR Pump-Probe Spectroscopy. PHYSICAL REVIEW LETTERS, 103, 123005.
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Kheifets, A. S., Naja, A., Casagrande, E. M. S., & Lahmam-Bennani, A. (2009). An energetic (e, 2e) reaction away from the Bethe ridge: recoil versus binary. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(16).
Résumé: We analyse the recoil-to-binary (RB) peak intensity ratio in an energetic (e, 2e) reaction performed on the valence ns sub-shell of noble gas atoms away from the Bethe ridge condition. A qualitative change in the RB ratio dependence on the ejected electron energy from He to Ar can be explained by the variation of reflectivity of the short-range Hartree-Fock potential. The reflectivity increases profoundly from lighter (He) to heavier (Ne and Ar) noble gas atoms because of modification of the scattering phases due to occupation of the target p orbitals (Levinson-Seaton theorem). This effect is further modified due to strong inter-shell correlations in Ar. These theoretical predictions are confirmed experimentally.
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Khemliche, H., Rousseau, P., Roncin, P., Etgens, V. H., & Finocchi, F. (2009). Grazing incidence fast atom diffraction: An innovative approach to surface structure analysis. Appl. Phys. Lett., 95(15), 151901.
Résumé: An alternative diffraction technique, based on grazing incidence scattering of high energy atoms, is applied to surface structure determination of crystalline surfaces. This technique, named GIFAD for grazing incidence fast atom diffraction, uses the same geometry as reflection high energy electron diffraction but is less invasive, more surface sensitive, and readily interpretable quantitatively. We present here a demonstration of this approach on a prototypical II-VI compound, ZnSe(001). Besides providing lattice parameter with high accuracy, we show that GIFAD gives straightforward access to the surface valence electron density profile, allowing clear identification of an electron transfer from Zn to Se. (C) 2009 American Institute of Physics. [doi:10.1063/1.3246162]
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Lacombe, S., & Le Sech, C. (2009). Advances in radiation biology: Radiosensitization in DNA and living cells. SURFACE SCIENCE, 603(10-12), 1953–1960.
Résumé: One fundamental goal of radiation biology is the evolution of concepts and methods for the elaboration of new approaches and protocols for the treatment of cancers. In this context, the use of fast ions as ionizing particles offers the advantage of optimizing cell killing inside the tumor whilst preserving the surrounding healthy tissues. One extremely promising strategy investigated recently is the addition of radiosensitizers in the targeted tissue. The optimization of radiotherapy with fast ions implies a multidisciplinary approach to ionizing radiation effects on complex living systems, ranging from studies on single molecules to investigations of entire organisms. In this article we review recent studies on ion induced damages in simple and complex biological systems, from DNA to living cells. The specific aspect of radiosensitization induced by metallic atoms is described. As a fundamental result, the addition of sensitizing compounds with ion irradiation may improve therapeutic index in cancer therapy. In conclusion, new perspectives are proposed based on the experience and contribution of different communities including Surface Sciences, to improve the development of radiation biology. (C) 2009 Elsevier B.V. All rights reserved.
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Lafosse, A., Bertin, M., & Azria, R. (2009). Electron driven processes in ices: Surface functionalization and synthesis reactions. PROGRESS IN SURFACE SCIENCE, 84(5-6), 177–198.
Résumé: The ability to control and orientate chemical reactivity in the condensed phase is a major challenge of modern research. Upon interaction with condensed molecules electrons drive bond cleavage thus generating a population of very reactive species in the condensed medium. These reactive species may interact either within the volume leading to the synthesis of new molecules or with the substrate surface by forming strong chemical bonds. The former reaction is known as electron induced synthesis and the latter one as electron induced surface functionalization. High-energy electrons achieve only a low chemical specificity due to the large number of dissociating open channels. in contrast, electrons with energies below ionization threshold of the irradiated matter are capable of high selectivity because of the dissociative electron attachment mechanism. In this review recent studies of electron interaction with condensed molecules on hydrogenated diamond substrates will be described. In particular electron induced functionalization of diamond surfaces by CH(2)CN groups, decarboxylation reactions in condensed films of pure organic acids RCOOH (R = H, CH(3), C(2)H(5), CFA carbamic acid formation in CO(2):NH(3), HCOOH:NH(3) and CF(3)COOH:NH(3) binary ice mixtures, and glycine formation in a CH(3)COOD:NH(3) Mixture are presented and discussed. (c) 2009 Elsevier Ltd. All rights reserved.
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Lafosse, A., Bertin, M., Hoffman, A., & Azria, R. (2009). Surface functionalization by low-energy electron processing of molecular ices. SURFACE SCIENCE, 603(10-12), 1873–1877.
Résumé: Low-energy electron processing of condensed molecular films (also called ices) is an efficient method to induce functionalization of a substrate, and thereby to modify and adjust its electronic and chemical properties. This method takes advantage of a resonant mechanism specific to low-energy electrons (by opposition to photons), the dissociative electron attachment (DEA), the key process allowing the chemical selectivity to be directly and easily controlled by the kinetic energy of the processing electrons. The functionalization procedure is described and illustrated by high resolution electron energy loss spectroscopy (HREELS) results on the induced anchoring of CH(2)CN organic chains on synthetic diamond by electron irradiation at 2 eV of condensed acetonitrile. The range of application of the proposed functionalization method is worth to be extended to other organic/inorganic interfaces, such as organic layers on metallic and semiconducting substrates. (C) 2009 Elsevier B.V. All rights reserved.
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Lahmam-Bennani, A., Casagrande, E. M. S., & Naja, A. (2009). Experimental investigation of the triple differential cross section for electron impact ionization of N-2 and CO2 molecules at intermediate impact energy and large ion recoil momentum. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(23).
Résumé: The (e, 2e) triple differential cross sections (TDCS) are measured for the ionization of nitrogen and carbon dioxide molecules in a coplanar asymmetric geometry for a wide range of ejected electron energies and at an incident energy about 500-700 eV. This kinematics corresponds to a large momentum imparted to the ion, and is meant to enhance the recoil scattering. The experimental binary and recoil angular distributions of the TDCS are characterized both by a shift towards larger angles with respect to the momentum transfer direction and by a large intensity in the recoil region, in particular for the ionization of the 'inner' N-2(2 sigma(g)) molecular orbital. The data are compared with the results of calculations using the first Born approximation-two centre continuum (FBA-TCC) theoretical model for treating differential electron impact ionization. The experimentally observed shifts and recoil intensity enhancement are not predicted by the model calculations, which rather yield a TDCS symmetrically distributed around the momentum transfer direction, and completely fail in describing the recoil distribution. It is hoped that these new results will stimulate the development of more refined theories for correctly modelling single ionization of molecules.
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Lahmam-Bennani, A., Naja, A., Casagrande, E. M. S., Okumus, N., Dal Cappello, C., Charpentier, I., & Houamer, S. (2009). Dynamics of electron impact ionization of the outer and inner valence (1t(2) and 2a(1)) molecular orbitals of CH4 at intermediate and large ion recoil momentum. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(16).
Résumé: The triply differential cross section has been measured for electron-impact ionization of the outer valence 1t(2) and the inner valence 2a(1) orbitals of methane using the (e,2e) technique with coplanar asymmetric kinematics. The measurements are performed at scattered electron energy of 500 eV, ejected electron energy of 12, 37 and 74 eV and for scattering angle of the fast outgoing electron of 6 degrees. This kinematics is characterized by a target ion recoil momentum ranging from moderate (0.25 au) to very large (3.2 au) values. The results are compared with theoretical cross sections calculated using the 1CW and the BBK models recently extended to molecules. The experimental cross sections exhibit a very large recoil scattering, especially for the inner 2a(1) molecular orbital, which is not predicted by the theory. The differences between experiment and theory are attributed to the very strong scattering from the ion, not properly accounted for by theory. This indicates the need for further theoretical developments as well as experimental investigations in order to correctly model the process of molecular ionization.
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Laruelle, F., Boye-Peronne, S., Gauyacq, D., & Lievin, J. (2009). Revisiting Mulliken's Concepts about Rydberg States and Rydberg-Valence Interactions from Large-Scale Ab Initio Calculations on the Acetylene Molecule. JOURNAL OF PHYSICAL CHEMISTRY A, 113(47), 13210–13220.
Résumé: A quantitative characterization of the Rydberg and valence singlet electronic states of acetylene lying in the 5-10.7 eV region is performed by using large-scale ab initio calculations. A special attention is paid on the comparison between the present calculations and Mulliken's concepts for Rydberg states, based on single-electron and single-configuration description. Most of the properties of the Rydberg states have been qualitatively understood via this comparison, mainly shown by the shape and size of the outer Rydberg molecular orbital. More quantitatively, Rydberg-valence mixing has been evaluated in several excited energy regions, as for instance, the interaction between the (C) over tilde' (1 pi(g))(2) (1)A(g) doubly excited valence state and the manifold of electronic components of the np series, or the interaction between the (E) over tilde 1 pi(g) (1)B(u) valence state and the (F) over tilde 3d pi(g) (1)Sigma(+)(u) Rydberg state. The rapid predissociation of the lowest (C) over tilde 3s sigma (1)Pi(u) Rydberg state has been interpreted as a case of Rydbergization, earlier predicted by Mulliken.
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Le Barbu-Debus, K., Broquier, M., Mahjoub, A., & Zehnacker-Rentien, A. (2009). Chiral recognition in jet-cooled complexes of (1R,2S)-(+)-cis-1-amino-2-indanol and methyl lactate: on the importance of the CH...pi interaction. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(35), 7589–7598.
Résumé: Complexation between (1R,2S)-(+)-cis-1-amino-2-indanol (AI) and the two enantiomers of methyl lactate has been studied by means of laser-induced fluorescence, resonance-enhanced two-photon ionisation, and IR-UV double resonance spectroscopy, in the region of 3 μm. Two isomeric complexes have been spectroscopically characterised for each diastereoisomer. Comparison with ab initio calculations shows that the most stable form is an insertion structure, common to the two diastereoisomers, in which the OH group of methyl lactate inserts into the intramolecular bond of AI. This structure shows almost no chiral discrimination. A secondary structure has been observed, which is specific to each enantiomer. It involves a main hydrogen bond from the OH group of methyl lactate to AI together with weaker hydrogen bonds, which depend on chirality. The enantioselectivity in the hydrogen bond topology is due to a weak stabilizing CH center dot center dot center dot pi interaction, involving the CH located on the asymmetric carbon of methyl lactate, which can be obtained for one of the enantiomers only.
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Le Lay, G., Aufray, B., Leandri, C., Oughaddou, H., Biberian, J. P., De Padova, P., Davila, M. E., Ealet, B., & Kara, A. (2009). Physics and chemistry of silicene nano-ribbons. APPLIED SURFACE SCIENCE, 256(2), 524–529.
Résumé: We review our recent discovery of silicene in the form of silicon nano-ribbons epitaxially grown on silver (1 1 0) or (1 0 0) surfaces, which paves the way for the growth of graphene-like sheets. We further draw some perspectives for this unique novel material upon mild hydrogenation. (C) 2009 Elsevier B.V. All rights reserved.
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Le Moal, E., Fort, E., & Leveque-Fort, S. (2009). Metallic films and nanostructures for molecular fluorescence enhancement. ACTUALITE CHIMIQUE, (332), 36–44.
Résumé: Metallic films and nanostructures for molecular fluorescence enhancement Molecule fluorescence is subject to the influence of its direct electromagnetic environment. Excitation and emission processes can be modified by the presence of a metallic structure, due to interference phenomena and coupling to surface plasmon modes. Metallic films ranging in morphology from nanoparticles to percolated, continuous, plane and rough films were designed and characterized. Their influence on the optical behaviour of the fluorophores was investigated by experiments and a theoretical model, as a function of fluorophore-to-metal distance and molecular orientation. The detected signal is found to be amplified by one to two orders of magnitude. Moreover, fluorophore photostabilization and the modification of intermolecular energy transfer processes are reported. This paper demonstrates the interest in this technology for sensitivity improvement of DNA chip and for applications in cell and tissue imaging.
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Le Moal, E., Leveque-Fort, S., Potier, M. - C., & Fort, E. (2009). Nanoroughened plasmonic films for enhanced biosensing detection. Nanotechnology, 20(22), 225502.
Résumé: Although fluorescence is the prevailing labeling technique in biosensing applications, sensitivity improvement is still a striving challenge. We show that coating standard microscope slides with nanoroughened silver films provides a high fluorescence signal enhancement due to plasmonic interactions. As a proof of concept, we applied these films with tailored plasmonic properties to DNA microarrays. Using common optical scanning devices, we achieved signal amplifications of more than 40-fold.
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Lebech, M., Houver, J. C., & Dowek, D. (2009). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. I. Ion-electron kinetic energy correlation and laboratory frame photoemission. JOURNAL OF CHEMICAL PHYSICS, 130(19), 194307.
Résumé: The (V(A+), V(e), e) vector correlation method, combining imaging and time-of-flight resolved electron-ion coincidence techniques, is used to probe dissociative photoionization (DPI) of CO induced by vacuum ultra violet linearly or circularly polarized synchrotron radiation in the 26-33 eV photon excitation energy range. It provides original information about both the photoionization dynamics of the CO molecule and the dissociation dynamics of the CO(+) molecular ions. The explored region corresponds to valence and inner-valence CO(+) ionic states, which involve doubly or multiply excited electronic configurations. In this paper I we identify up to 17 DPI reaction pathways by the position of the intermediate CO(+) molecular states in the Franck-Condon region and the (C(+) + O) or (O(+) + C) dissociation limits to which they correlate. For these processes we report the laboratory frame beta(C+/O+) and beta(e) asymmetry parameters as well as the relative branching ratios in selected binding energy bands. The I(chi,theta(e),phi(e)) molecular frame photoelectron angular distributions for selected PI processes will be reported in a companion paper II and compared with multichannel Schwinger configuration interaction ab initio calculations of these observables.
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Lefebvre, R., & Atabek, O. (2009). Unusual low-intensity regime in laser-induced molecular photodissociation. International Journal of Quantum Chemistry, 109, 3423.
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Lefebvre, R., Atabek, O., Šindelka, M., & Moiseyev, N. (2009). Resonance Coalescence in Molecular Photodissociation. PHYSICAL REVIEW LETTERS, 103(12), 123003.
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Lepere, V., Picard, Y. J., Barat, M., Fayeton, J. A., Lucas, B., & Beroff, K. (2009). Photodissociation dynamics of Ar2(+) and Ar3(+) excited by 527 nm photons. J Chem Phys, 130(19), 194301.
Résumé: The photofragmentation dynamics of Ar(2)(+) and Ar(3)(+) clusters has been investigated at a 527 nm wavelength (2.35 eV) using a setup that allows simultaneous detection of the ionic and neutral fragments in a coincidence experiment. Measurement of positions and times of flight enables in principle a complete description of the fragmentation dynamics. The photofragmentation dynamics of Ar(3)(+) clusters is similar to that of Ar(2)(+) with, in addition, the ejection of a third fragment that can be neutral or ionized via a resonant electron capture. This is attributed to the triangular geometry of the Ar(3)(+) ion.
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Lorente, N., & Gauyacq, J. - P. (2009). Efficient Spin Transitions in Inelastic Electron Tunneling Spectroscopy. Phys. Rev. Lett., 103(17), 176601.
Résumé: The excitation of the spin degrees of freedom of an adsorbed atom by tunneling electrons is computed using strong coupling theory. Recent measurements [Heinrich et al., Science 306, 466 ( 2004)] reveal that electron currents in a magnetic system efficiently excite its magnetic moments. Our theory shows that the incoming electron spin strongly couples with that of the adsorbate so that memory of the initial spin state is lost, leading to large excitation efficiencies. First-principles transmissions are evaluated in quantitative agreement with the experiment.
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M.Ziegler, J. K., R.Berndt, A.G.Borisov et J.P.Gauyacq. (2009). Linewidth of a cesium adatom resonance on Ag(111). Phys. Rev. B, 79, 075401.
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Mahjoub, A., Chakraborty, A., Lepere, V., Le Barbu-Debus, K., Guchhait, N., & Zehnacker, A. (2009). Chirality-dependent hydrogen bond direction in jet-cooled (S)-1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM): IR-ion dip vibrational spectroscopy of the neutral and the ion. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(25), 5160–5169.
Résumé: The structural modifications of (S)-1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM) upon ionisation have been investigated in jet-cooled conditions, by means of laser-induced fluorescence, REMPI, and IR-UV ion-dip spectroscopy of the neutral ground state and the ion. These results combined with ab initio calculations, support the presence in the jet of two low-energy conformers of THIQM. In the most stable Conformer I, the CH(2)OH substituent acts as a hydrogen bond donor to the nitrogen lone pair in the equatorial position. In this case, the nitrogen atom is in ( S) configuration. Conformer II shows the opposite NH center dot center dot center dot O hydrogen bond from the hydrogen atom in the equatorial position of nitrogen to the OH group. In this case, the nitrogen atom is in ( R) configuration. This chirality dependence of the hydrogen bond direction is lost upon ionisation. While ionisation of Conformer II reinforces the NH center dot center dot center dot O hydrogen bond, ionisation of Conformer I induces its isomerisation to the same ion as Conformer II, i.e. a change in hydrogen bond direction.
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Millone, M. A. D., Hamoudi, H., Rodriguez, L., Rubert, A., Benitez, G. A., Vela, M. E., Salvarezza, R. C., Gayone, J. E., Sanchez, E. A., Grizzi, O., Dablemont, C., & Esaulov, V. A. (2009). Self-Assembly of Alkanedithiols on Au(111) from Solution: Effect of Chain Length and Self-Assembly Conditions. LANGMUIR, 25(22), 12945–12953.
Résumé: A comparative study on the adsorption of buthanedithiol (BDT). hexanedithiol (HDT), and nonanedithiol (NDT) oil Au(111) from ethanolic and n-hexane solutions and two different preparation procedures is presented. SAM characterization is based oil reflection-absorption infrared spectroscopy, electrochemistry, X-ray photoelectron spectroscopy, and time of flight direct recoil spectroscopy. Results indicate that one can obtain a standing-Up phase of dithiols and that the amount of the precursor lying-down phase decreases from BDT to NDT, irrespective of the solvent and self-assembly conditions. A good ordering of the hydrocarbon chains in the standing-up configuration is observed for HDT and NDT when the system is prepared in degassed n-hexane with all operations carried out in the dark. Disulfide bridges at the free SH terminal groups are formed for HDT and to a lesser extent for NDT prepared in ethanol in the presence of oxygen, but We found no evidence of ordered multilayer formation in our experiments. No disulfides were observed for BDT that only forms the lying-clown phase. Our results demonstrate the key role of the chain length and the procedure (solvent nature and oxygen presence) in controlling the surface structure and chemistry of SAMs dithiols on Au(111).
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Milman, P., Keller, A., Charron, E., & Atabek, O. (2009). Molecular orientation entanglement and temporal Bell-type inequalities. EUROPEAN PHYSICAL JOURNAL D, 53, 383.
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Morisset, S., Ferro, Y., & Allouche, A. (2009). Isotopic effects in the sticking of H and D atoms on the (0001) graphite surface. CHEMICAL PHYSICS LETTERS, 477(1-3), 225–229.
Résumé: A quantum study of the sticking of hydrogen and deuterium atoms chemisorbed onto graphite (0001) surface is carried out in the collinear scattering approximation, taking into account the phonon modes of the system. The sticking coefficients are calculated for hydrogen and deuterium atoms with incident energies ranging from 0.17 to 0.22 eV, for surface temperatures of 10 and 150 K. The calculation of the sticking coefficients of H and D evidenced an isotopic effect which is discussed. (C) 2009 Elsevier B.V. All rights reserved.
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Nave, S., & Jackson, B. (2009). Methane dissociation on Ni(111) and Pt(111): Energetic and dynamical studies. JOURNAL OF CHEMICAL PHYSICS, 130(5).
Résumé: Electronic structure studies and quantum scattering methods are used to elucidate the differing reactivities of methane on Ni(111) and Pt(111). For both surfaces the lowest energy pathway to dissociation is over the top site, where the static surface barrier to reaction is about 0.14 eV lower on Pt(111) than on Ni(111). If allowed to relax, both surfaces exhibit a puckering of the metal atoms in the vicinity of the adsorbates and at the transition state. Thus, motion of the lattice can change the barrier to reaction. A quantum model for dissociation is employed that includes several molecular coordinates, and allows for coupling to the lattice motion and puckering of the lattice. We find that on Ni(111) the lattice has time to pucker, increasing the reactivity relative to the static surface case. The more massive atoms on the Pt(111) surface do not have time to pucker during the reaction. As both lattices become vibrationally excited the reactivity increases significantly, particularly at low incident energies where tunneling dominates. Our model suggests that tunneling is important for these large barrier systems, particularly at the relatively low incident energies of the experiments. Our work also suggests that at the large nozzle temperatures of the experiments, there are contributions to the total reactivity from vibrationally excited molecules, particularly for Ni(111). Our model is in reasonable agreement with the experimental results for Ni(111), while we significantly underestimate the reactivity on Pt(111) as well as the difference in reactivity between Ni(111) and Pt(111). This may result from errors in our total-energy calculations and/or effects due to motion (tunneling) of the methyl group at the transition state.
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Parent, P., Bournel, F., Lasne, J., Lacombe, S., Strazzulla, G., Gardonio, S., Lizzit, S., Kappler, J. - P., Joly, L., Laffon, C., & Carniato, S. (2009). The irradiation of ammonia ice studied by near edge x-ray absorption spectroscopy. JOURNAL OF CHEMICAL PHYSICS, 131(15), 154308.
Résumé: A vapor-deposited NH(3) ice film irradiated at 20 K with 150 eV photons has been studied with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen K-edge. Irradiation leads to the formation of high amounts (12%) of molecular nitrogen N(2), whose concentration as a function of the absorbed energy has been quantified to 0.13 molecule/eV. The stability of N(2) in solid NH(3) has been also studied, showing that N(2) continuously desorbs between 20 and 95 K from the irradiated ammonia ice film. Weak concentrations (<1%) of other photoproducts are also detected. Our NEXAFS simulations show that these features own to NH(2), N(2)H(2), and N(3)(-).
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Pirali, O., Tokaryk, D. W., & Vervloet, M. (2009). Vibrational dependence of the rotational, spin-orbit splitting, and lambda-doubling parameters in the C ''(5)Pi(ui) state of N-2. CANADIAN JOURNAL OF PHYSICS, 87(5), 601–606.
Résumé: We have recorded the high-resolution emission spectrum of the Herman infrared band (C ''(5)Pi(ui)-A'(5)Sigma(+)(g)) system of N-2 in the 8000-15000 cm(-1) range from an experimental set-up coupling a corona discharge with a supersonic expansion. The analysis of four new bands has permitted us to determine spectroscopic parameters of the nu' = 0 and nu' = 1 vibrational levels of the C ''(5)Pi(ui) state and to study the vibrational dependence of the molecular parameters over the range nu' = 0 to v' = 4. In particular, the values of the spin-orbit coupling and the Lambda-doubling parameters are discussed.
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Pirali, O., Vervloet, M., Mulas, G., Malloci, G., & Joblin, C. (2009). High-resolution infrared absorption spectroscopy of thermally excited naphthalene. Measurements and calculations of anharmonic parameters and vibrational interactions. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(18), 3443–3454.
Résumé: We report in this paper the recording and analysis of the vibrational spectrum of naphthalene in the 1.6-200 μm (50-6000 cm(-1)) spectral range with a resolution of 0.005 cm(-1). The spectrum, recorded at room temperature, shows several complex structures in the Q branches of the c-type bands, which can be assigned to hot-band sequences as well as combination bands and overtones. To analyse the experimental data, we developed a model based on anharmonic calculations which predicts the transitions (positions and intensities) involving the vibrational levels populated at room temperature. This work permits us to estimate the validity and limitations of our calculations, which can be used to predict the band profiles of naphthalene (and larger PAHs) at various temperatures, with potential astrophysical applications.
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Riedel, D., Bocquet, M. L., Lesnard, H., Lastapis, M., Lorente, N., Sonnet, P., & Dujardin, G. (2009). Selective Scanning Tunnelling Microscope Electron-induced Reactions of Single Biphenyl Molecules on a Si(100) Surface. J. Am. Chem. Soc., 131(21), 7344–7352.
Résumé: Selective electron-induced reactions of individual biphenyl molecules adsorbed in their weakly chemisorbed configuration on a Si(100) surface are investigated by using the tip of a low-temperature (5 K) scanning tunnelling microscope (STM) as an atomic size source of electrons. Selected types of molecular reactions are produced, depending on the polarity of the surface voltage during STM excitation. At negative surface voltages, the biphenyl molecule diffuses across the surface in its weakly chemisorbed configuration. At positive surface voltages, different types of molecular reactions are activated, which involve the change of adsorption configuration from the weakly chemisorbed to the strongly chemisorbed bistable and quadristable configurations. Calculated reaction pathways of the molecular reactions on the silicon surface, using the nudge elastic band method, provide evidence that the observed selectivity as a function of the surface voltage polarity cannot be ascribed to different activation energies. These results, together with the measured threshold surface voltages and the calculated molecular electronic structures via density functional theory, suggest that the electron-induced molecular reactions are driven by selective electron detachment (oxidation) or attachment (reduction) processes.
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Riedel, D., Cranney, M., Martin, M., Guillory, R., Dujardin, G., Dubois, M., & Sonnet, P. (2009). Surface-Isomerization Dynamics of trans-Stilbene Molecules Adsorbed on Si(100)-2x1. J. Am. Chem. Soc., 131(15), 5414–5423.
Résumé: Photoinduced trans-cis isomerization studies of stilbene molecules in the gas phase have led to a precise understanding of the corresponding molecular dynamics. Yet, when such molecules are adsorbed on surfaces, these reactions are expected to be strongly modified as compared to what is know in the gas phase. In this work, a low temperature (5 K) scanning tunneling microscope (STM) is used to image the trans-stilbene molecules deposited on a Si(100)-2x1 surface at 12 K. trans-Stilbene undergoes conformational changes during the adsorption process such that four different stilbene conformers are observed: trans-stilbene (TS), cis-stilbene (CS), and two new conformers I(1) and I(2). Furthermore, electronic excitation of individual stilbene molecules, by means of tunnel electrons, is shown to activate specific reversible molecular surface isomerization (TS <-> I(1) and CS <-> I(2)) combined with diffusion across the surface. Calculated STM topographies, using the tight binding method, indicate that the CS and TS molecules are physisorbed. The molecular conformations of the surface isomers I(1) and I(2) are suggested to be analogous to transient states conformations of the stilbene molecule when stabilized by the silicon surface. The measurements of the molecular surface isomerization and diffusion reaction yields are used to build a qualitative potential energy surface of the various stilbene reactions. The molecular surface-isomerization dynamics is shown to be influenced by the type of dopant (n or p). This is related to surface charging, which reveals modifications in the stilbene ionization potential.
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Riedel, D., Delacour, C., Mayne, A. J., & Dujardin, G. (2009). Very low thermally induced tip expansion by vacuum ultraviolet irradiation in a scanning tunneling microscope junction. Phys. Rev. B, 80(15), 155451.
Résumé: The thermal and photoelectronic processes induced when a vacuum ultraviolet (VUV) laser irradiates the junction of a scanning tunneling microscope (STM) are studied. This is performed by synchronizing the VUV laser shots with the STM scan signal. Compared to other wavelengths, the photoinduced thermal STM-tip expansion is not observed when the VUV radiation is freed from spurious emissions. Furthermore, we demonstrate that the purified VUV photoinduced transient signal detected in the tunnel current is entirely due to photoelectronic emission and not combined with thermionic processes. The ensuing photoelectron emission is shown to be independent of the tip-surface distance while varying linearly with the pure VUV laser intensity. These results illustrate a strong decoupling between phonons and photoelectrons which allows a very weak STM-tip expansion.
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Schmidt, T. W., Pino, T., & Brechignac, P. (2009). The C-H Stretch Intensities of Polycyclic Aromatic Hydrocarbon Cations. Origins and Astrophysical Implications. JOURNAL OF PHYSICAL CHEMISTRY A, 113(15), 3535–3541.
Résumé: Infrared vibrational transition intensities of polycyclic aromatic hydrocarbons are known to depend strongly on the charge state. The detailed understanding of this effect for the C-H stretching modes has been approached by applying the quantum theory of atoms in molecules. Several benchmark calculations were undertaken in order to disentangle charge and size effects, from benzene (C(6)H(6)) up to the ovalene (C(32)H(14)) molecule. Upon decomposition of the dipole moment derivative along a C-H stretch into charge, charge flux, and dipole flux terms, it is found that it is the competition between the sum of the first two terms and the latter which drives the intensity, due to their opposing signs. Additionally, while the dipole flux term changes very little with size and charge, the other terms are strongly sensitive to these. This effect leads to a very weak C-H stretch intensity for cation sizes close to pyrene (C(16)H(10)) and comparable intensities between neutral and cations for the much larger ones. The astrophysical implications are discussed.
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Serkovic Loli, L. N., Hamoudi, H., Esteban Gayone, J., Luz Martiarena, M., Sanchez, E. A., Grizzi, O., Pasquali, L., Nannarone, S., Doyle, B. P., Dablemont, C., & Esaulov, V. A. (2009). Growth of N,N '-Bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxdiimide Films on Ag (111). JOURNAL OF PHYSICAL CHEMISTRY C, 113(41), 17866–17875.
Résumé: We have studied the self-assembly characteristics, the electronic structure, and the thermal stability of thin N,N'-bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) films grown on Ag (111) by a broad set of surface science analysis techniques. The deposition of single molecules to the formation of very thin films performed at room temperature under ultrahigh-vacuum (UHV) conditions was followed by atomic force microscopy (AFM), scanning tunneling microscopy (STM), ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS), and was modeled by density functional theory (DFT) calculations. STM pictures show that substrate step edges are the starting point for molecule adsorption, which is followed by formation of islands and eventually a monolayer. The monolayer is composed of large domains with ordered molecules with their perylene-3,4,9,10-tetracarboxdiimide (PTCDI) core lying almost parallel to the surface. For further exposure, multilayer stacked domains are formed. For thicker films molecular order could not be established. Upon heating it is found that the multilayer is stable up to 150 degrees C where a rapid desorption takes place, followed by the dissociation of the molecules, leaving an ordered monolayer of presumably perylene core type molecules.
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Serkovic Loli, L. N., Sanchez, E. A., Gayone, E., Grizzi, O., & Esaulov, V. A. (2009). Assembly and thermal stability of thin EP-PTCDI films on Ag(111). PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(20), 3849–3853.
Résumé: We report a multi-technique study of the adsorption kinetics and self-assembly characteristics of EP-PTCDI grown on Ag(111) at UHV conditions and room temperature. Changes in the valence band characteristics for the mono and the multilayer film and the stability as a function of the annealing temperature are discussed. The results show that the molecules start to adsorb on the step edges forming ordered islands that grow to fully cover a monolayer. Further exposure results in the stacking of similarly ordered islands of several layers. The desorption experiment shows that the film is stable up to 150 degrees C where a rapid desorption of the multilayer takes place, followed by a decomposition of the molecules for temperatures higher than 170 degrees C.
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Shafizadeh, N., Soep, B., Mestdagh, J. M., & Breckenridge, W. H. (2009). Charge transfer in metal-atom-containing molecules in the gas phase. INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY, 28(3), 359–406.
Résumé: The presence of charge transfer (CT) is ubiquitous in metal-atom-containing molecules in the gas phase. The states of interest range from ground states to the lower excited states, given the generally low ionisation potentials of metal atoms. This review is written from an experimentalist's perspective, to describe the specifics of CT states in stable molecules containing a metal atom or of transient CT states in dynamical processes. The large body of experimental evidence allows the description of such states in an empirical or semi-empirical manner, including partial point charges and polarised electron clouds on the ions. These simple models are compared with more quantitative models, allowing the development of sophisticated descriptions. The simple perspective deriving from experimental evidence is justified, when it is possible via accurate quantum calculations and allows building a rather complete framework for the ionic bond or CT-induced dynamics.
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Teperik, T. V., & Borisov, A. G. (2009). Optical resonances in the scattering of light from a nanostructured metal surface: A three-dimensional numerical study. Phys. Rev. B, 79(24), 245409.
Résumé: We present the full three-dimensional numerical study of the scattering of light by the gold substrate composed of square periodic array of inverted pyramidal pits. The time-dependent wave-packet-propagation approach was used to extract the complete scattering matrix as well as the near fields. The role of the pit-localized and surface-supported plasmonic modes in resonant reflection spectra and field enhancement is revealed. We show that the resonances in the specular reflection arise because of the excitation of the pit-localized plasmons while resonant absorption is linked with excitation of the surface-plasmon polaritons. For certain structure parameters absorption can reach 100%. Our theoretical results are in a good agreement with recently published experimental data [N. M. B. Perney , Opt. Express 14, 847 (2006); Phys. Rev. B 76, 035426 (2007)]. We also show that present structure allows one to obtain zero specular reflection where all scattered intensity is redirected into the grazing beams.</p>.
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Tiwari, A. K., Nave, S., & Jackson, B. (2009). Methane Dissociation on Ni(111): A New Understanding of the Lattice Effect. PHYSICAL REVIEW LETTERS, 103(25), 253201.
Résumé: The nature of the lattice motion during the dissociation of methane on Ni(111) is analyzed in great detail, and various models for including lattice effects are explored. It is shown that the thermal vibrations of the lattice strongly modify the reactivity, but that the lattice motion is relatively unperturbed by the incident molecule during the collision, in contrast with several earlier predictions. Based on these studies we propose a new model to describe the effects of lattice motion, which agrees well with exact quantum calculations.
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Tranvouez, E., Boer-Duchemin, E., Mayne, A. J., Vanderbruggen, T., Scheele, M., Cartwright, R., Comtet, G., Dujardin, G., Schneegans, O., Chretien, P., & Houze, F. (2009). Influence of morphology on the conductance of single-crystal diamond surfaces measured by atomic force microscopy. J. Appl. Phys., 106(5), 054301.
Résumé: A detailed atomic force microscopy (AFM) study of the conductance of hydrogenated single-crystal diamond (100) surfaces over submicron length scales is presented. The hydrogenation process was found to influence the surface morphology by reducing surface roughness, with the subsequent appearance of small triangular structures (with side lengths of 200 nm). Conducting AFM measurements revealed variations in the current and resistance that were related to the topography. Possible explanations include surface inhomogeneity of the electronic structure or variations in the contact resistance due to the surface roughness.
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Tranvouez, E., Orieux, A., Boer-Duchemin, E., Devillers, C. H., Huc, V., Comtet, G., & Dujardin, G. (2009). Manipulation of cadmium selenide nanorods with an atomic force microscope. Nanotechnology, 20(16), 165304.
Résumé: We have used an atomic force microscope (AFM) to manipulate and study ligand-capped cadmium selenide nanorods deposited on highly oriented pyrolitic graphite (HOPG). The AFM tip was used to manipulate (i.e., translate and rotate) the nanorods by applying a force perpendicular to the nanorod axis. The manipulation result was shown to depend on the point of impact of the AFM tip with the nanorod and whether the nanorod had been manipulated previously. Forces applied parallel to the nanorod axis, however, did not give rise to manipulation. These results are interpreted by considering the atomic-scale interactions of the HOPG substrate with the organic ligands surrounding the nanorods. The vertical deflection of the cantilever was recorded during manipulation and was combined with a model in order to estimate the value of the horizontal force between the tip and nanorod during manipulation. This horizontal force is estimated to be on the order of a few tens of nN.
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Vizzini, S., Oughaddou, H., Hoarau, J. Y., Biberian, J. P., & Aufray, B. (2009). Y Growth of ultrathin film aluminum oxide on Ag(111). APPLIED PHYSICS LETTERS, 95(17), 173111.
Résumé: Scanning tunneling microscopy (STM) and spectroscopy and electron energy loss spectroscopy were used to characterize ultrathin epitaxial aluminum oxide on Ag(111) which was prepared via a specific deposition and oxidation process. Atomically resolved STM images show self-organized oxide stripes of 4 nm width with excellent homogeneity in depth and chemical composition properties which are crucial for applications of this oxide to magnetic tunnel junctions. We also found that electrons tunnel easily through the oxide film. This oxide has a different spectroscopic signature from that of alumina and has a wide bandgap close to 6.6 eV. (C) 2009 American Institute of Physics. [doi:10.1063/1.3251778]
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Zugarramurdi, A., Zabala, N., Silkin, V. M., Borisov, A. G., & Chulkov, E. V. (2009). Lifetimes of quantum well states and resonances in Pb overlayers on Cu(111). Phys. Rev. B, 80(11), 115425.
Résumé: We present results of calculations of the lifetimes of excited electrons (holes) in quantum well states and quantum well resonances in Pb overlayers supported on Cu(111). Many-body decay via inelastic energy relaxation and one-electron decay via energy-conserving one-electron transfer into the substrate are considered. One-electron energies and wave functions have been computed for different coverages of the Pb overlayer (from 1 to 18 monolayers) by using a one-dimensional pseudopotential for the entire overlayer-substrate system in the framework of density functional theory within the local density approximation. The elastic (energy-conserving resonant electron transfer) contribution to the total lifetime broadening of quantum well resonances has been calculated within the wave packet propagation method. The inelastic electron-electron (many-body) contribution to the lifetime broadening of both occupied and unoccupied quantum well states has been evaluated using GW approximation. The decay mechanisms of both quantum well states and quantum well resonances in thick overlayers are discussed.
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Actes de Conférences |
Bundaleski, N., Khemliche, H., Rousseau, P., Cassimi, A., Maunoury, L., & Roncin, P. (2009). Discharging dynamics of insulator surfaces irradiated by highly charged ions. In 14TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF HIGHLY CHARGED IONS (HCI 2008) (Vol. 163, 012091).
Résumé: Guiding and focusing of keV to MeV ions by insulator micro-capillaries offer exciting perspectives for the production of low divergence micro-sized beams and the spatial control over the irradiated zone. These effects result from the local charging of the capillary inner wall and depend strongly on the charging/discharging dynamics of the insulating material. This dynamics has been studied on various glass insulator surfaces (borosilicate, fused silica and quartz) by grazing incidence highly charged ion beams. We propose simple experimental methods to derive the relevant time constant and study the influence of temperature and different material properties to the charging process.
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Cassimi, A., Maunoury, L., Muranaka, T., Huber, B., Dey, K. R., Lebius, H., Lelievre, D., Ramillon, J. M., Been, T., Ikeda, T., Kanai, Y., Kojima, T. M., Iwai, Y., Yamazaki, Y., Khemliche, H., Bundaleski, N., & Roncin, P. (2009). Imaging dynamics of charge-auto-organisation in glass capillaries. In NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS (Vol. 267, pp. 674–677).
Résumé: Multiply charged ion beam transmission through insulating capillaries is today a very active field of research. Thanks to the work of several groups during the last five years, several features of this unexpected process have been evidenced. The open challenge is to understand and control the self-organized charging-up of the capillary walls, which leads finally to the ion transmission. Up to now, the specific charge distribution on the inner surface, as well as the dynamics of the build-up, are still to be understood. While capillaries usually studied are microscopic pore networks etched in different materials, our concern is in macroscopic single capillaries made of glass. With a length of several centimeters and a diameter of a few micrometers at the exit, these capillaries have nevertheless the same aspect ratio as the etched pores (length/diameter approximate to 100). One of the leading goals of this research on single capillaries is to produce multi-charged ion beams with diameters smaller than a micrometer (nano-beams). These glass capillaries offer the opportunity to be used as an ion funnel due to their amazing proper-ties of guiding and focusing highly charged ion beams without altering neither their initial charge state nor the beam emittance (<10(-3) pi mm mrad). However, the understanding of the underlying process is not complete and relies on models assuming charge patches distributed along the capillary and which still need to be tested. We present the first observation imaging the dynamics of the charging-up process in single glass capillaries. During the build-up of the self-organized charge deposition on the capillary walls, the 230 keV Xe(23+) transmitted beam is deflected back and forth several times as the outgoing current increases. This is in agreement with the picture of charge patches created sequentially along the capillary and thus deflecting the beam until a stationary state is reached. (C) 2008 Elsevier B.V. All rights reserved.
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Colgan, J., Reddish, T. J., Huetz, A., Bolognesi, P., Avaldi, L., Gisselbrecht, M., Lavollee, M., & Pindzola, M. S. (2009). The 'KER' effect in the double photoionization of H(2). In INTERNATIONAL CONFERENCE ON MANY PARTICLE SPECTROSCOPY OF ATOMS (Vol. 141).
Résumé: Recent experimental and theoretical work examining the double photoionization of H(2) has uncovered surprising changes in the fully differential cross sections as a function of the kinetic energy released to the protons (which is equivalent to different internuclear separations of the molecule). We describe the recent joint theoretical and experimental investigations which have uncovered the physical reasons for this phenomenon. We show that the observed variations are solely due to the epsilon(Sigma) component of the polarization vector along the molecular axis. Our conclusions are supported by further investigations of the photoionization of H(2)(+), in which similar dramatic variations in the photoelectron angular distributions for the sigma(g) -> sigma(u) transition are found as the internuclear separation is varied. The angular distributions for the sigma(g) -> pi(u) transition show little dependence on the internuclear separation.
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Goddet, J. P., Sebban, S., Guilbaud, O., Gautier, J., Zeitoun, P., Valentin, C., Tissandier, F., Marchenko, T., Lambert, G., Nejdl, J., Cros, B., Maynard, G., Robillard, B., Kazamias, S., Cassou, K., Klisnick, A., Ros, D., Benredjem, J., Mocek, T., Kozlova, M., & Jakubczak, K. (2009). Characterization of a Seeded Optical-Field Ionized Collisional Soft X-Ray Laser. In X-RAY LASERS 2008 (Vol. 130, pp. 135–142). Springer Proceedings in Physics, 130.
Résumé: By seeding ail optical-field-ionized population inverted plasma amplifier with the 25th harmonic of an infrared laser we have produced a compact, diffraction-limited and Fourier-limited laser beam in the soft x-ray spectral range. This laser beam is emitted within a cone of 0.7 mrad at a repetition rate of 10 Hz at a central wavelength of 32.8 nm, The beam exhibits a regular Gaussian spatial profile, and wavefront distortions smaller than lambda/17. The measured coherence time of 5.5 ps is equal to the duration of the lifetime of the amplifying plasma which shows that this source has reached the Fourier limit.
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Guilbaud, O., Goddet, J. P., Sebban, S., Joyeux, D., Ros, D., Gautier, J., Cassou, K., Kazamias, S., Klisnick, A., Habib, J., Zeitoun, P., Benredjem, D., de Rossi, S., Maynard, G., Cros, B., Boudaa, A., Phalippou, D., & Calisti, A. (2009). Temporal Coherence and Spectral Linewidth of a Seeded Soft X-Ray Laser Pulse. In X-RAY LASERS 2008 (Vol. 130, pp. 193–198). Springer Proceedings in Physics, 130.
Résumé: We present in this paper the first measurement of the spectral profile of a seeded soft x-ray laser. Using a varying path difference interferometer the temporal coherence of a seeded OFI x-ray laser has been experimentally determined, leading to a coherence length of 5ps of the order of the gain lifetime. The measured bandwidth is of order 3.4 m angstrom which is in good agreement with the prediction of a theoretical model presented here.
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Habib, J., Klisnick, A., Guilbaud, O., Joyeux, D., Zielbauer, B., Kazamias, S., Ros, D., de Dortan, F., & Pittman, M. (2009). Temporal Coherence and Spectral Line Shape of a GRIP Transient X-Ray Laser. In X-RAY LASERS 2008 (Vol. 130, pp. 115–121).
Résumé: We have used a variable path-difference, wavefront-division interferometer to measure the temporal coherence of an unseeded Ni-like Mo GRIP X-ray laser. This quantity is inversely related to its spectral linewidth. We have investigated the role of several pump parameters on the inferred spectral width. Along this experiment, particular attention has been paid on the source stability.
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Klisnick, A., Larroche, O., De Dortan, F., Habib, J., Guilbaud, O., Kazamias, S., Ros, D., & Zielbauer, B. (2009). Recent Developments on Seeded or Unseeded Transient X-Ray Lasers. In X-RAY LASERS 2008 (Vol. 130, pp. 221–229).
Résumé: The COLAX code was used to investigate the role of several parameters oil the spatial and temporal behaviour of the output pulse of a transient X-ray laser seeded by a harmonic pulse. The importance of the collisional linewidth oil the duration of the output pulse is underlined.
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Margarone, D., Kozlova, M., Nejdl, J., Rus, B., Mocek, T., Homer, P., Polan, J., Stupka, M., Jamelot, G., Cassou, K., Kazamias, S., Klisnick, A., Ros, D., Bercegol, H., Danson, C., & Hawkes, S. (2009). Laser-induced damage studies in optical elements using X-ray laser interferometric microscopy. In DAMAGE TO VUV (Vol. 7361, 73610N). Proceedings of SPIE, 7361.
Résumé: Results of a novel X-ray laser application, aimed at understanding the microscopic effects involved in formation of laser-induced damage in optical materials exposed to sub-ns laser pulses, will be presented. Specifically, we studied thin plane beamsplitters that are presently the weakest element of the next generation of high-energy lasers (LMJ, NIF), with permanent damage threshold below 20 J/cm(2). Standard fused silica substrates and a model system, containing well-defined micron grooves as seeding sites to trigger damage when irradiated by 438 nm laser pulses, were in situ probed by a neon-like zinc X-ray laser delivering up to 10 mJ at 21.2 nm. The probing beamline employed a double Lloyd's mirror interferometer, used in conjunction with an imaging mirror to provide magnification of similar to 8. In conjunction with an array of in-situ optical diagnostics, one of the questions addressed was whether the damage (transient or permanent) on the rear surface of the beamsplitter occurs during or after the laser pulse, i.e. whether it is due to local electrical fields or to other processes. Another issue, examined by both the X-ray interferometric microscopy and the optical diagnostics, is whether a local rear-surface modification is associated with non-linear effects (self-focusing, filamentation) of the laser beam in the bulk.
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Ros, D., Kazamias, S., Guilbaud, O., Habib, J., Zielbauer, B., Pittman, M., Jamelot, G., Klisnick, A., Lagron, J. - C., Joyeux, D., de Rossi, S., Delmotte, F., Lacombe, S., Porcel, E., Lesech, C., Penhoat, A. M., & Touati, A. (2009). Recent Advances on LASERIX Facility: Development of XUV Sources System and Applications. Perspectives from 2008 to 2010. In X-RAY LASERS 2008 (Vol. 130, pp. 13–22).
Résumé: LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam that could also be used to produce synchronized XUV sources. This experimental configuration highly enhances the scientific opportunities of the facility, giving thus the opportunity to realize both X-ray laser experiments and more generally pump/probe experiments, mixing IR and XUV sources. In this contribution, the main results concerning both the development of XUV sources (in the seeded or ASE mode) and their use for applications (irradiation of DNA samples) are presented.
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Rottke, H., Guyetand, O., Gisselbrecht, M., Huetz, A., Agostini, P., Carre, B., Breger, P., Gobert, O., Garzella, D., Hergott, J. - F., Tcherbakoff, O., Merdji, H., Bougeard, M., Boettcher, M., Zhavoronkov, N., Ansari, Z., Sandner, W., Antoine, P., & DiMauro, L. F. (2009). Photoionization in combined ultra short XUV and infrared laser pulses. In INTERNATIONAL CONFERENCE ON MANY PARTICLE SPECTROSCOPY OF ATOMS (Vol. 141).
Résumé: Multi-photon-double ionization of xenon by Ti:Sapphire laser pulses combined with their 25(th) harmonic has been studied by means of a momentum imaging spectrometer. The determination of the momenta of the emitted photoelectron pair and of its energy and angular correlation gives insight into the various mechanisms leading to double ionization. Although the conditions for non sequential direct multi-photon double ionization are met in the experiment, it is found that two-step sequential processes prevail.
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Roy, P., Brubach, J. B., Manceron, L., Rouzieres, M., Pirali, O., & Tchana, F. K. (2009). The AILES Beam line for THz and IR spectroscopy. In TERAHERTZ AND MID INFRARED RADIATION: BASIC RESEARCH AND PRACTICAL APPLICATIONS (pp. 63–64).
Résumé: The new infrared beamline (AILES) at the third generation Synchrotron Radiation source SOLEIL is now 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 of the beamline offers high flux and brilliance for all kinds of infrared experiments. We will briefly review the main research themes and future developments of coherent emission at SOLEIL.
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Zielbauer, B., Habib, J., Kazamias, S., Guilbaud, O., Pittman, M., Ros, D., du Penhoat, M. - A. H., Touati, A., Le Sech, C., Porcel, E., & Lacombe, S. (2009). Strand Breaks in DNA Samples Induced with LASERIX. In X-RAY LASERS 2008 (Vol. 130, pp. 409–415).
Résumé: Samples of plasmid DNA were irradiated with pulsed 18.9 nm radiation originating from a Mo X-ray laser pumped in GRIP configuration at the LASERIX facility [1]. Surface doses of up to 500 kGray were delivered with a repetition rate of 10 Hz and average pulse energy of 200 nJ. The occurrence of single and double strand breaks not present in controls having undergone the same treatment except for the XRL irradiation can be seen as a clear effect of the XRL irradiation. This confirms the role of direct effects in DNA damages as previously seen with low energy ions [2, 3] and electrons.
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