Peer-reviewed Publications |
Al Shorman, M. M., Gharaibeh, M. F., Bizau, J. M., Cubaynes, D., Guilbaud, S., El Hassan, N., Miron, C., Nicolas, C., Robert, E., Sakho, I., Blancard, C., & McLaughlin, B. M. (2013). K-shell photoionization of Be-like and Li-like ions of atomic nitrogen: experiment and theory. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 46(19), 195701.
Résumé: Absolute cross sections for the K-shell photoionization of Be-like and Li-like atomic nitrogen ions were measured by employing the ion-photon merged-beam technique at the SOLEIL synchrotron radiation facility in Saint-Aubin, France. High-resolution spectroscopy at nominal resolutions of 38, 56, 111, 133 meV full width at half maximum (FWHM) for Be-like and 125 meV FWHM for Li-like atomic nitrogen ions was achieved for the photon energies ranging from 410 up to 460 eV. The experimental measurements are compared with theoretical estimates from the multi-configuration Dirac-Fock, R-matrix and an empirical method. The interplay between experiment and theory enabled the identification and characterization of the strong 1s -> 2p resonances features observed in the K-shell spectra of each ion and the region around 460 eV for the 1s -> 3p resonance of the N3+ ion yielding suitable agreement with experiment.
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Alata, I., Bert, J., Broquier, M., Dedonder, C., Feraud, G., Gregoire, G., Soorkia, S., Marceca, E., & Jouvet, C. (2013). Electronic Spectra of the Protonated Indole Chromophore in the Gas Phase. J. Phys. Chem. A, 117, 4420–4427.
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Aldeek, F., Schneider, R., Fontaine-Aupart, M. - P., Mustin, C., Lecart, S., Merlin, C., & Block, J. - C. (2013). Patterned Hydrophobic Domains in the Exopolymer Matrix of Shewanella oneidensis MR-1 Biofilms. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 79(4), 1400–1402.
Résumé: Water-dispersible amphiphilic surface-engineered quantum dots (QDs) were found to be strongly accumulated within discrete zones of the exopolymer network of Shewanella oneidensis MR-1 biofilms, but not on the cell surfaces. These microdomains showed a patterned distribution in the exopolymer matrix, which led to a restricted diffusion of the amphiphilic nanoparticles.
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Altnöder J., B. A., Lee J.J., Otto K.E., Suhm M.A., Zehnacker-Rentien A. (2013). Chirality-dependent balance between hydrogen bonding and London dispersion in isolated (±)-1-indanol clusters. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10167–10180.
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Atabek, O., Lefebvre, R., Jaouadi, A., & Desouter-Lecomte, M. (2013). Proposal for laser purification in molecular vibrational cooling using zero-width resonances. PHYSICAL REVIEW A, 87, 031403.
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Azzam, A. A. A., Yurchenko, S. N., Tennyson J., Martin-Drumel, M. A., & & Pirali, O. (2013). Terahertz spectroscopy of hydrogen sulfide. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 130, 341–351.
Résumé: Pure rotational transitions of hydrogen sulfide (H2S) in its ground and first excited vibrational states have been recorded at room temperature. The spectrum comprises an average of 1020 scans at 0.005 cm−1 resolution recorded in the region 45–360 cm−1 (1.4 to 10.5 THz) with a globar continuum source using a Fourier transform spectrometer located at the AILES beamline of the SOLEIL synchrotron. Over 2400 rotational lines have been detected belonging to ground vibrational state transitions of the four isotopologues H232S, H233S, H234S, and H236S observed in natural abundance. 65% of these lines are recorded and assigned for the first time, sampling levels as high as J=26 and Ka=17 for H232S. 320 pure rotational transitions of H232S in its first excited bending vibrational state are recorded and analysed for the first time and 86 transitions for H234S, where some of these transitions belong to new experimental energy levels. Rotational constants have been fitted for all the isotopologues in both vibrational states using a standard effective Hamiltonian approach. Comprehensive comparisons are made with previously available data as well as the data available in HITRAN, CDMS, and JPL databases. The 91 transitions assigned to H236S give the first proper characterization of its pure rotational spectrum.
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Barry, C. S., Cocinero, E. J., Carcabal, P., Gamblin, D. P., Stanca-Kaposta, E. C., Remmert, S. M., Fernandez-Alonso, M. C., Rudic, S., Simons, J. P., & Davis, B. G. (2013). 'Naked' and Hydrated Conformers of the Conserved Core Pentasaccharide of N-linked Glycoproteins and Its Building Blocks. Journal Of The American Chemical Society, 135(45), 16895–16903.
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Bellec, A., Chaput, L., Dujardin, G., Riedel, D., Stauffer, L., & Sonnet, P. (2013). Reversible charge storage in a single silicon atom. Phys. Rev. B, 88(24), 241406.
Résumé: The ultimate miniaturization of electronic devices at the atomic scale with single electrons requires controlling the reversible charge storage in a single atom. However, reversible charge storage is difficult to control as usually only one charge state can be stabilized. Here, combining scanning tunneling microscopy (STM) and density functional theory (DFT), we demonstrate that a single silicon dangling bond of a hydrogenated p-type doped Si(100) surface has two stable charge states (neutral and negatively charged) at low temperature (5 K). Reversible charge storage is achieved using a gate electric field between the STM tip and the surface.
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Bergeron, H., Curado, E. M. F., Gazeau, J. P., & Rodrigues, L. M. C. S. (2013). Symmetric generalized binomial distributions. Journal of Mathematical Physics, 54(12), 123301.
Résumé: In two recent articles, we have examined a generalization of the binomial distribution associated with a sequence of positive numbers, involving asymmetric expressions of probabilities that break the symmetry win-loss. We present in this article another generalization (always associated with a sequence of positive numbers) that preserves the symmetry win-loss. This approach is also based on generating functions and presents constraints of non-negativeness, similar to those encountered in our previous articles. (C) 2013 AIP Publishing LLC.
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Bergeron, H., Gazeau, J. P., & Youssef, A. (2013). Are the Weyl and coherent state descriptions physically equivalent? PHYSICS LETTERS A, 377(8), 598–605.
Résumé: We investigate the consistency of coherent state quantization in regard to physical observations in the non-relativistic (or Galilean) regime. We compare this particular type of quantization of the complex plane with the canonical (Weyl) quantization and examine whether they are or not equivalent in their predictions. As far as only usual dynamical observables (position, momentum, energy, ...) are concerned, the quantization through coherent states is proved to be a perfectly valid alternative. We successfully put to the test the validity of CS quantization in the case of data obtained from vibrational spectroscopy. (C) 2013 Elsevier B.V. All rights reserved.
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Beroff, K., Chabot, M., Martinet, G., Pino, T., Bouneau, S., Le Padellec, A., Feraud, G., Do Thi, N., Calvo, F., Bordas, C., & Lepine, F. (2013). Anion production in high-velocity cluster-atom collisions; the electron capture process revisited. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 46(1), 015201.
Résumé: Anion production cross sections in collisions between C-n(+), Cn carbon clusters (n <= 5) and helium atoms have been measured in high-velocity collisions (v = 2.25 and 2.6 au). This paper focuses on two of the three processes responsible for the C-n(-) production, namely double electron capture (DEC) onto C-n(+) cations and single electron capture onto neutral (SECN) C-n. They were experimentally distinguished from a gaseous thickness dependence study. Dissociative and non-dissociative cross sections were measured and, in the case of DEC, all dissociative branching ratios measured; for these small systems, the C-2(-) fragment was found magical. Data concerning electron capture in neutral-neutral collisions are extremely rare, especially at high velocity. Introduction of this measured process in the independent atom and electron (IAE) model allowed us to revisit and satisfactorily reproduce the so-far unexplained size evolution of single electron capture (SEC) cross sections in 2.6 au C-n(+)-He (n <= 10) collisions (Chabot et al 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2593-603). IAE calculations for DEC cross sections and their comparison with experiment suggest a loss of electron in anionic C-n(-) species after the collision, competing with fragmentation and depending on the size.
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Bobrov, K., & Guillemot, L. (2013). Autocatalytic effect of Cu nano-islands on the reaction of water with the oxygen covered Cu(110) surface. Surface Science, 611, 32–39.
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Bomme, C., Guillemin, R., Marin, T., Journel, L., Marchenko, T., Dowek, D., Trcera, N., Pilette, B., Avila, A., Ringuenet, H., Kushawaha, R. K., & Simon, M. (2013). Double momentum spectrometer for ion-electron vector correlations in dissociative photoionization. REVIEW OF SCIENTIFIC INSTRUMENTS, 84(10), 103104.
Résumé: We have developed a new momentum spectrometer dedicated to momentum vector correlations in the context of deep core photoionization of atomic and molecular species in the gas phase. In this article, we describe the design and operation of the experimental setup. The capabilities of the apparatus are illustrated with a set of measurements done on the sulphur core 1s photoionization of gas-phase CS2. (C) 2013 AIP Publishing LLC.
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Bon, P., Barroca, T., Lévèque-Fort, S., & Fort, E. (2013). Label-free evanescent microscopy for membrane nano-tomography in living cells. Journal of Biophotonics, 7(11-12), 857–862.
Résumé: We show that through-the-objective evanescent microscopy (epi-EM) is a powerful technique to image membranes in living cells. Readily implementable on a standard inverted microscope, this technique enables full-field and real-time tracking of membrane processes without labeling and thus signal fading. In addition, we demonstrate that the membrane/interface distance can be retrieved with 10 nm precision using a multilayer Fresnel model. We apply this nano-axial tomography of living cell membranes to retrieve quantitative information on membrane invagination dynamics. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Borisov, A. G., Sanchez-Portal, D., Kazansky, A. K., & Echenique, P. M. (2013). Resonant and nonresonant processes in attosecond streaking from metals. Phys. Rev. B, 87(12), 121110.
Résumé: We report on the theoretical study of laser-assisted attosecond photoemission from metals. The full time-dependent quantum approach reveals the role of the resonant interband and nonresonant surface emission processes in formation of final atto-streaking spectra. The present results explain recent experimental data on magnesium and show that the valence band streaking essentially reflects the respective weight of surface and resonant bulk electron ejection. DOI: 10.1103/PhysRevB.87.121110
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Boudon, V., Asselin, P., Soulard, C., Goubet, M., Huet, A., Georges, R., Pirali, O., & & Roy, P. (2013). High-Resolution Spectroscopy and Analysis of the v2 + v3 Combination Band of SF6 in a Supersonic Jet Expansion. MOLECULAR PHYSICS, 111(14-15), 2154–2162.
Résumé: Sulphur hexafluoride is a very strong greenhouse gas whose concentration is increasing in the atmosphere. It is detected through infrared absorption spectroscopy in the strong ν3 fundamental region. Due to the existence of low-lying vibrational states of this molecule, however, many hot bands arise at room temperature and those are still not known. We present here a contribution to the elucidation of this hot band structure, by analysing the ν2 + ν3 combination band. We use a supersonic jet expansion high-resolution spectrum at a rotational temperature of ca. 25 K that was recorded thanks to the Jet-AILES setup at the Source Optimisée de Lumière d’Energie Intermédiaire du LURE (SOLEIL) Synchrotron. The simplified structure of this cold spectrum allowed us to assign 444 rovibrational lines and to fit effective Hamiltonian parameters, leading to a very satisfactory spectrum simulation. The parameters obtained in this way allow to calculate the spectrum of the ν3+ν2−ν2 hot band.
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Calisti A., F. S., Mossé C., Talin B., Klisnick A., Meng L., Benredjem D., Guilbaud O. (2013). Line Profiles of Ni-like Collisional XUV Laser Amplifiers: Particle Correlation Effects. HEDP, 9(3), 516–522.
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Calvo, F., Falvo, C., & Parneix, P. (2013). A simple but accurate potential for the naphthalene-argon complex: Applications to collisional energy transfer and matrix isolated IR spectroscopy. JOURNAL OF CHEMICAL PHYSICS, 138(3), 034305.
Résumé: An explicit polarizable potential for the naphthalene-argon complex has been derived assuming only atomic contributions, aiming at large scale simulations of naphthalene under argon environment. The potential was parametrized from dedicated quantum chemical calculations at the CCSD(T) level, and satisfactorily reproduces available structural and energetic properties. Combining this potential with a tight-binding model for naphthalene, collisional energy transfer is studied by means of dedicated molecular dynamics simulations, nuclear quantum effects being accounted for in the path-integral framework. Except at low target temperature, nuclear quantum effects do not alter the average energies transferred by the collision or the collision duration. However, the distribution of energy transferred is much broader in the quantum case due to the significant zero-point energy and the higher density of states. Using an ab initio potential for the Ar-Ar interaction, the IR absorption spectrum of naphthalene solvated by argon clusters or an entire Ar matrix is computed via classical and centroid molecular dynamics. The classical spectra exhibit variations with growing argon environment that are absent from quantum spectra. This is interpreted by the greater fluxional character experienced by the argon atoms due to vibrational delocalization. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773469]
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Canario, A. R., L. Guillemot, J. Diaz-Valdés, J.E. Valdés, P. Vargas, & V.A. Esaulov. (2013). Electron transfer and energy loss processes in fluorine scattering on oxygen covered Ag (110) – crystal azimuthal dependence. NIM B, 315, 36–41.
Résumé: Measurements of energy-losses and electron transfer processes in 1 to 4 keV fluorine ions and atoms scattering on clean and oxygen covered Ag(110) were studied. We report data for surface channeling conditions for different surface azimuths for the clean and oxygen covered O(2×1)–Ag(110) (2x1) reconstructed surface. Adsorption of oxygen results in strong changes in energy losses and a decrease in the negative ion fraction. Energy loss results are discussed in the light of calculations using non-linear models for stopping power, ab initio crystal structure calculations of the electronic density and semi-classical deterministic simulations.
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Canepa M., M. G., Chiara T., Cavalleri O., Prato M., Chaudhari V.R. and Esaulov V.A. (2013). Spectroscopic ellipsometry of Self assembled Monolayers: interface effects. The case of phenyl selenide SAMs on gold. PCCP, 15, 11559–11565.
Résumé: This work focuses on the quantitative application of spectroscopic ellipsometry to the study of optical properties and thickness of self assembled monolayers (SAMs) of phenyl selenide SAMs deposited from the liquid phase on gold. STM, XPS and cyclic voltammetry measurements provide additional chemical and morphological characterization of the SAMs. While routine ellipsometry analysis of SAMs often relies on the film-induced δΔ change of the Δ ellipsometric angle and discard SAM-substrate interface effects, the present data show a distinctive behaviour of the δΨ data that we assign to interface effects, stronger than those previously found for densely packed alkanethiols SAMs. An inaccurate modelling of the variations of Ψ related to the nano-structured SAM-substrate interface leads to a large overestimation of the film thickness. A simple model, accounting effectively for the interface layer between the film and the substrate and for the molecular optical absorptions, provides a good agreement with the data and a reliable thickness estimate of the SAM.
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Capello, M. C., Broquier, M., Dedonder-Lardeux, C., Jouvet, C., & Pino, G. A. (2013). Fast excited state dynamics in the isolated 7-azaindole-phenol H-bonded complex. J Chem Phys, 138(5), 054304.
Résumé: The excited state dynamics of the H-bonded 7-azaindole-phenol complex (7AI-PhOH) has been studied by combination of picosecond pump and probe experiments, LIF measurements on the nanosecond time scale and ab initio calculations. A very short S(1) excited state lifetime (30 ps) has been measured for the complex upon excitation of the 0(0)(0) transition and the lifetime remains unchanged when the nu(6) vibrational mode (0(0)(0) + 127 cm(-1)) is excited. In addition, no UV-visible fluorescence was observed by exciting the complex with nanosecond pulses. Two possible deactivation channels have been investigated by ab initio calculations: first an excited state tautomerization assisted by a concerted double proton transfer (CDPT) and second an excited state concerted proton electron transfer (CPET) that leads to the formation of a radical pair (hydrogenated 7AIH() radical and phenoxy PhO() radical). Both channels, CDPT and CPET, seem to be opened according to the ab initio calculations. However, the analysis of the ensemble of experimental and theoretical evidence indicates that the excited state tautomerization assisted by CDPT is quite unlikely to be responsible for the fast S(1) state deactivation. In contrast, the CPET mechanism is suggested to be the non-radiative process deactivating the S(1) state of the complex. In this mechanism, the lengthening of the OH distance of the PhOH molecule induces an electron transfer from PhOH to 7AI that is followed by a proton transfer in the same kinetic step. This process leads to the formation of the radical pair (7AIH()...PhO()) in the electronically excited state through a very low barrier or to the ion pair (7AIH(+)...PhO(-)) in the ground state. Moreover, it should be noted that, according to the calculations the pisigma* state, which is responsible for the H loss in the free PhOH molecule, does not seem to be involved at all in the quenching process of the 7AI-PhOH complex.
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Carcabal, P., Cocinero, E. J., & Simons, J. P. (2013). Binding energies of micro-hydrated carbohydrates: measurements and interpretation. CHEMICAL SCIENCE, 4(4), 1830–1836.
Résumé: The strength of the interaction between three monosaccharides (O-phenyl-beta-D-gluco-, beta-D-galacto-and alpha-D-mannopyranoside) and a single water molecule has been investigated experimentally in the gas phase by means of 2-colour UV-UV ionisation and dissociation threshold measurements. Their binding energies have also been calculated using dispersion corrected DFT methods and the resolution of identity approximation. The calculated and experimental relative binding energies are in good correspondence at all considered levels of theory, and the RI-B97D+ disp/ TZVPP level of theory in particular, provides very good agreement with a considerable reduction in computational time. Although these systems experience some conformational changes upon photo-ionisation, the experimental measurements lead to reliable estimates of the binding energies of the different conformers of the monosaccharide-water complexes and their relative values reflect their structural differences.
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Carpentier, Y., Pino, T., & Bréchignac, P. (2013). R2PI Spectroscopy of Aromatic Molecules Produced in an Ethylene-Rich Flame. JOURNAL OF PHYSICAL CHEMISTRY A, 117(39), 10092–10104.
Résumé: Laser spectroscopy, combined with mass spectrometry, was applied to study the spectra of aromatic molecules produced in a premixed ethylene-rich flat flame. These studies produce new gas-phase electronic spectra of polyaromatic compounds, which ultimately will guide the understanding of the chemical processes that lead to polycyclic aromatic hydrocarbon (PAH) growth or PAH formation locking. Resonant two-photon ionization (R2PI) spectra of all species detectable in a specific fuel-rich flame were recorded simultaneously during a single scan of the laser wavelength, within the 220–330 nm range. Comparison with spectra available in the literature allowed us to identify 16 aromatic species. In the PAH forming region of this flame, we found that the main PAHs are accompanied by a great diversity of other species, including in particular various side-chains on aromatic networks. We also show that this technique allows, at least in some cases, to distinguish between different isomers associated with the same mass peak, although the extracted PAHs are only cooled down to room temperature.
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Carré B., Poisson, L., Shafizadeh, N., & Soep, B. (2013). Stereodynamics of Chemical Reactions. Journal of Chemical Physics A, 117, 8093–8094.
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Chabot M., Beroff K., Gratier P., Jallat A., & Wakelam V. (2013). Reactions forming C(0;+) n=2;10, Cn=2;4H(0;+) and C3H(0;+) 2 in the gas phase: semi empirical branching ratios. The Astrophysical Journal, 771(90), 1–13.
Résumé: The aim of this paper is to provide a new set of branching ratios for interstellar and planetary chemical networks based on a semi empirical model. We applied, instead of zero order theory (i.e. only the most exoergic decaying channel is considered), a statistical microcanonical model based on the construction of
breakdown curves and using experimental high velocity collision branching ratios for their parametrization. We applied the model to ion-molecule, neutral-neutral, and ion-pair reactions implemented in the few popular databases for astrochemistry such as KIDA, OSU and UMIST. We studied the reactions of carbon and hydrocarbon species with electrons, He+, H+, CH+, CH, C, and C+ leading to intermediate
complexes of the type Cn=2;10, Cn=2;4H, C3H2, C+n =2;10, Cn=2;4H+, or C3H+2. Comparison of predictions with measurements supports the validity of the model. Huge deviations with respect to database values are often obtained. E ects of the new branching ratios in time dependant chemistry for dark clouds and for photodissociation region chemistry with conditions similar to those found in the Horsehead Nebula are discussed.
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Charron, E., & Sukharev, M. (2013). Non-Hermitian wave packet approximation of Bloch optical equations. J. Chem. Phys., 138, 024108.
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Dartois E., Engrand C., Brunetto R., Duprat J., Pino T., Quirico E., Remusat L., Bardin N., Briani G., Mostefaoui S., Morinaud G., Crane B., S. N., Delauche L., Jamme F., Sandt Ch., & Dumas P. (2013). UltraCarbonaceous Antarctic micrometeorites, probing the Solar System beyond the nitrogen snow-line. ICARUS, 1(224), 243–252.
Résumé: The current Solar System architecture is a heritage of the protoplanetary disk that surrounded the young Sun, 4.56 Gy ago. Primitive extraterrestrial objects provide means to trace back the primordial composition and radial distribution of matter in this disk. Here, we present a combined micro-IR, Raman, chemical and isotopic study of two ultracarbonaceous micrometeorites recovered from Antarctica (UCAMMs). This study reveals particles containing an unusually high nitrogen- and deuterium-rich organic matter analogous to a polyaromatic hydrogenated carbon nitride, characterized by nitrogen concentration with bulk atomic N/C ratios of 0.05 and 0.12 (locally exceeding 0.15). We propose that such nitrogen-rich carbonaceous material can be formed by energetic irradiations of nitrogen-rich ices in very low temperature regions of the Solar System. Such conditions are encountered at the surface of small objects beyond the trans-neptunian region. UCAMMs provide unique insights on physico-chemical processes that occurred beyond the nitrogen snow-line, revealing organic material from the extreme outer regions of the Solar System that cannot be investigated by remote sensing methods.
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Dartois, E., Ding, J. J., de Barros, A. L. F., Boduch, P., Brunetto, R., Chabot, M., Domaracka, A., Godard, M., Lv, X. Y., Guaman, C. F. M., Pino, T., Rothard, H., da Silveira, E. F., & Thomas, J. C. (2013). Swift heavy ion irradiation of water ice from MeV to GeV energies. Approaching true cosmic ray compaction. ASTRONOMY & ASTROPHYSICS, 557, A97.
Résumé: Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles in space. One of the primary structural changes induced is the loss of porosity, and the mantles evolve toward a more compact amorphous state. Previously, ice compaction was monitored at low to moderate ion energies. The existence of a compaction threshold in stopping power has been suggested.
Aims. In this article we experimentally study the effect of heavy ion irradiation at energies closer to true cosmic rays. This minimises extrapolation and allows a regime where electronic interaction always dominates to be explored, providing the ice compaction cross section over a wide range of electronic stopping power.
Methods. High-energy ion irradiations provided by the GANIL accelerator, from the MeV up to the GeV range, are combined with in-situ infrared spectroscopy monitoring of ice mantles. We follow the IR spectral evolution of the ice as a function of increasing fluence (induced compaction of the initial microporous amorphous ice into a more compact amorphous phase). We use the number of OH dangling bonds of the water molecule, i.e. pending OH bonds not engaged in a hydrogen bond in the initially porous ice structure as a probe of the phase transition. These high-energy experiments are combined with lower energy experiments using light ions (H, He) from other facilities in Catania, Italy, and Washington, USA.
Results. We evaluated the cross section for the disappearance of OH dangling bonds as a function of electronic stopping power. A cross-section law in a large energy range that includes data from different ice deposition setups is established. The relevant phase structuring time scale for the ice network is compared to interstellar chemical time scales using an astrophysical model.
Conclusions. The presence of a threshold in compaction at low stopping power suggested in some previous works seems not to be confirmed for the high-energy cosmic rays encountered in interstellar space. Ice mantle porosity or pending bonds monitored by the OH dangling bonds is removed efficiently by cosmic rays. As a consequence, this considerably reduces the specific surface area available for surface chemical reactions.
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Datta, D., Shen, J., & Esaulov, V. A. (2013). Hydrogen negative ion formation on a graphite HOPG surface. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and , 315, 42–44.
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Debnath, A., Falvo, C., & Meier, C. (2013). State-Selective Excitation of the CO Stretch in Carboxyhemoglobin by Mid-IR Laser Pulse Shaping: A Theoretical Investigation. JOURNAL OF PHYSICAL CHEMISTRY A, 117, 12884−12888.
Résumé: We present simulations of the excitation of specific vibrational levels of
the CO stretch in carboxyhemoglobin by shaped mid-IR laser pulses. The pulses are
calculated using local control theory, adapted to account for the protein fluctuations, which are included using a microscopic model developed previously. We show that efficient selective vibrational state preparation can be obtained, despite the presence of the fluctuations and orientational averaging, and can be monitored using transient absorption spectra. The mid-IR pulses are found to be in a realistic intensity regime and might soon be available by IR pulse shaping. This opens the way to a direct monitoring of vibrational relaxation from individually prepared, high-lying vibrational states of complex systems.
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Dehon, C., Soorkia, S., Pedrazzani, M., Jouvet, C., Barat, M., Fayeton, J. A., & Lucas, B. (2013). Photofragmentation at 263 nm of small peptides containing tyrosine: role of the charge transfer on CO. Phys. Chem. Chem. Phys., 15, 8779–8788.
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Dhahri, S., Ramonda, M., & Marliere, C. (2013). In-Situ Determination of the Mechanical Properties of Gliding or Non-Motile Bacteria by Atomic Force Microscopy under Physiological Conditions without Immobilization. Plos One, 8(4), e61663.
Résumé: We present a study about AFM imaging of living, moving or self-immobilized bacteria in their genuine physiological liquid medium. No external immobilization protocol, neither chemical nor mechanical, was needed. For the first time, the native gliding movements of Gram-negative Nostoc cyanobacteria upon the surface, at speeds up to 900 μm/h, were studied by AFM. This was possible thanks to an improved combination of a gentle sample preparation process and an AFM procedure based on fast and complete force-distance curves made at every pixel, drastically reducing lateral forces. No limitation in spatial resolution or imaging rate was detected. Gram-positive and non-motile Rhodococcus wratislaviensis bacteria were studied as well. From the approach curves, Young modulus and turgor pressure were measured for both strains at different gliding speeds and are ranging from 20 +/- 3 to 105 +/- 5 MPa and 40 +/- 5 to 310 +/- 30 kPa depending on the bacterium and the gliding speed. For Nostoc, spatially limited zones with higher values of stiffness were observed. The related spatial period is much higher than the mean length of Nostoc nodules. This was explained by an inhomogeneous mechanical activation of nodules in the cyanobacterium. We also observed the presence of a soft extra cellular matrix (ECM) around the Nostoc bacterium. Both strains left a track of polymeric slime with variable thicknesses. For Rhodococcus, it is equal to few hundreds of nanometers, likely to promote its adhesion to the sample. While gliding, the Nostoc secretes a slime layer the thickness of which is in the nanometer range and increases with the gliding speed. This result reinforces the hypothesis of a propulsion mechanism based, for Nostoc cyanobacteria, on ejection of slime. These results open a large window on new studies of both dynamical phenomena of practical and fundamental interests such as the formation of biofilms and dynamic properties of bacteria in real physiological conditions.
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Douce T., Eckstein A., Walborn S. P., Khoury A. Z., Ducci S., Keller A., Coudreau T., & Milman P. (2013). Direct measurement of the biphoton Wigner function through two-photon interference. Scientific Reports, 3, 3530.
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Falvo, C., Friha, H., Pino, T., Dhaouadi, Z., Parneix, P., Calvo, F., & and Brechignac, P. (2013). Effects of hydrogen dissociation on the infrared emission spectra of naphthalene: theoretical modeling. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10241–10250.
Résumé: The IR emission spectroscopy of naphthalene and its singly- and doubly-dehydrogenated radicals has been modeled using kinetic Monte Carlo simulations, taking into account the various relaxation pathways of radiative emission and hydrogen loss. Our modeling relies on quantum chemistry ingredients that were obtained from dedicated calculations based on density functional theory, including explicitly anharmonicity contributions. Our results show that the fragmentation products significantly contribute to the overall IR emission spectrum, especially to the intensity ratios between bands. Owing to the likely presence of polycyclic aromatic hydrocarbons in the interstellar medium, these findings are particularly relevant in the astrophysical context.
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Falvo, C., Debnath, A., and Meier, C. (2013). Vibrational ladder climbing in carboxy-hemoglobin: Effects of the protein environment. JOURNAL OF CHEMICAL PHYSICS, 138, 145101.
Résumé: We present simulations on vibrational ladder climbing in carboxy-hemoglobin. Motivated by recent experiments, we study the influence of different realistic pump probe parameters. To allow for a direct comparison with experimental results, transient absorption spectra obtained by a weak probe pulse following the strong, shaped pump pulse are calculated. The influence of the protein fluctuations is taken into account using a recently developed microscopic model. This model consists of a quantum Hamiltonian describing the CO vibration in carboxy-hemoglobin, together with a fluctuating potential, which is obtained by electronic structure calculation based on a large number of protein configurations. Using realistic pulse parameters, vibrational excitations to very high-lying states are possible, in qualitative agreement with experimental observations.
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Friha, H., Féraud, G., Troy, T., Falvo, C., Parneix, P., Bréchignac, P., Dhaouadi, Z., Schmidt, T. W., & Pino, T. (2013). Visible Photodissociation Spectra of the 1- and 2-Methylnaphthalene Cations: Laser Spectroscopy and Theoretical Simulations. JOURNAL OF PHYSICAL CHEMISTRY A, 117, 13664–13672.
Résumé: The electronic absorption spectra of the two methyl derivatives of the naphthalene cation were measured using an argon tagging technique. In both cases, a band system was observed in the visible range and assigned to the D2 ← D0 electronic transition. The 1-methylnaphthalene+ absorption bands revealed a red shift of 808 cm–1, relative to those of the naphthalene cation (14 906 cm–1), whereas for 2-methylnaphthalene+ a blue shift of 226 cm–1 appeared. A short vibrational progression, similar to the naphthalene cation, was also observed for both isomers and found to involve similar aromatic ring skeleton vibrations. Moreover, insights into the internal rotation motion of the methyl group were inferred, although the spectral resolution was not sufficient to fully resolve the substructure. These measurements were supported by detailed quantum chemical calculations. They allowed exploration of the potential energy curves along this internal coordinate, along with a complete simulation of the harmonic Franck–Condon factors using the cumulant Gaussian fluctuations formalism extended to include the internal rotation.
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Gans, B., Peng, Z., Carrasco, N., Gauyacq, D., Lebonnois, S., & Pernot, P. (2013). Impact of a new wavelength-dependent representation of methane photolysis branching ratios on the modeling of Titan's atmospheric photochemistry. ICARUS, 223(1), 330–343.
Résumé: A new wavelength-dependent model for CH4 photolysis branching ratios is proposed, based on the values measured recently by Gans et al. (Gans, B. et al. [2011]. Phys. Chem. Chem. Phys. 13,8140-8152). We quantify the impact of this representation on the predictions of a photochemical model of Titan's atmosphere, on their precision, and compare to earlier representations. Although the observed effects on the mole fraction of the species are small (never larger than 50%), it is possible to draw some recommendations for further studies: (i) the Ly-alpha branching ratios of Wang et al. (Wang, J.H. et al. [2000]. J. Chem. Phys. 113, 4146-4152) used in recent models overestimate the CH2:CH3 ratio, a factor to which a lot of species are sensitive; (ii) the description of out-of-Ly-alpha branching ratios by the “100% CH3” scenario has to be avoided, as it can bias significantly the mole fractions of some important species (C3H8); and (iii) complementary experimental data in the 130-140 nm range would be useful to constrain the models in the Ly-alpha deprived 500-700 km altitude range. (C) 2012 Elsevier Inc. All rights reserved.
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Garcia-Gil, S., Teillet-Billy, D., Rougeau, N., & Sidis, V. (2013). H Atom Adsorption on a Silicate Surface: The (010) Surface of Forsterite. JOURNAL OF PHYSICAL CHEMISTRY C, 117(24), 12612–12621.
Résumé: We present a first-principles computational study of the interaction of an H
atom with the (010) surface of forsterite (Mg2SiO4). Periodic DFT-GGA calculations (PBE)are carried out using the SIESTA code with core pseudopotentials and TZP localized basis sets. Potential energy curves are determined for the approach of the H atom toward different sites of the surface: atop, near, or in between the O, Mg, and Si atoms. An outer adsorption well is found for all investigated sites; it is deepest (162 meV) at a so-called “displaced Mg−O bridge” position. The binding at this well is of the “weak chemisorption”/“strongphysisorption” type. An inner stronger chemisorption well (670 meV deep) exists exclusivelynear an O site but not strictly atop. Depending on the path, we find activation barriers (25−170 meV high) against chemisorption, the lowest of these occurs for the top O site.General trends of the computed interaction energies qualitatively agree with the QM/MM results of Goumans et al. [Mon. Not. R. Astron. Soc. 2009, 393, 1403], but adsorption bindingenergies and barrier heights differ significantly.
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Gauyacq, J. P., & Lorente, N. (2013). Magnetic reversal of a quantum nanoferromagnet. PRB, 87(19), 195402.
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Gauyacq, J. P., Yaro, S. M., Cartoixa, X., & Lorente, N. (2013). Correlation-Mediated Processes for Electron-Induced Switching between Neel States of Fe Antiferromagnetic Chains. Phys. Rev. Lett., 110(8), 087201.
Résumé: The controlled switching between two quasistable Neel states in adsorbed antiferromagnetic Fe chains has recently been achieved by Loth et al. [Science 335, 196 (2012)] using tunneling electrons from an STM tip. In order to rationalize their data, we evaluate the rate of tunneling electron-induced switching between the Neel states. Good agreement is found with the experiment, permitting us to identify three switching mechanisms: (i) low STM voltage direct electron-induced transitions, (ii) intermediate STM voltage switching via spin-wave-like excitation, and (iii) high STM voltage transitions mediated by domain-wall formation. Spin correlations in the antiferromagnetic chains are the switching driving force, leading to a marked chain-size dependence. DOI: 10.1103/PhysRevLett.110.087201
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Gruet S., Morvan, A., Pirali O., Chamaillé T., Bouisset E., & Vervloet M. (2013). Fourier transform far-infrared spectroscopy of HN2+ on the AILES beamline of synchrotron SOLEIL. Canadian Journal of Physics, 91(11), 937–940.
Résumé: Nous présentons le spectre de rotation pure de HN2+ mesuré par spectroscopie d'absorption à transformée de Fourier (FT) dans le domaine spectral 20–40 cm–1. Les cations sont produits dans une cellule à décharge à cathode creuse refroidie a l'azote liquide, qui a été développée sur la ligne AILES du synchrotron SOLEIL. Le montage a été optimisé par la mesure des spectres de rotation–vibration de H3+ (bande ν2 centrée autour de 2521 cm–1), de HN2+ (bande ν1 centrée autour de 3234 cm–1), et de HCO+ (bande ν1 centrée autour de 3089 cm–1). Plusieurs raies de rotation–vibration ont été attribuées pour chaque ion et cinq transitions de rotation pure ont été identifiées pour HN2+. Ces résultats démontrent la faisabilité d'enregistrer des spectres de cations dans l'infrarouge lointain en utilisant une spectroscopie FT à large bande comme alternative aux techniques basées sur des lasers à fréquence ajustable.
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Ha-Thi M.H, Shafizadeh N., Poisson, L., & Soep, B. (2013). An Efficient Indirect Mechanism for the Ultrafast Intersystem Crossing in Copper Porphyrins. Journal of Chemical Physics A, 117, 8111–8118.
Résumé: The ultrafast dynamics of copper tetraphenylporphyrin (CuTPP), copper octaethylporphyrin (CuOEP) and of the free base tetraphenylporphyrin (H2TPP), excited in the S2. state have been investigated in the gas phase by femtosecond pump/probe experiments. The porphyrins were excited in the Soret band at 400 nm. Strikingly, the S2.-S1. internal conversion in H2TPP is very rapid (110 fs), as compared to that of ZnTPP (600 fs), previously observed. In turn, CuTPP and CuOEP, excited in S2., follow a different relaxation pathway from that of other open-shell metalloporphyrins. These two molecules exhibit a four-step decay ending on a slow evolution in the nanosecond range 2S2.→ 2CT→ 2T→ 2Ground State. This latter evolution is linked to the formation of the 2T, Tripdoublet state in CuTPP, observed in the condensed phase. It is shown that an intermediate charge transfer state plays a crucial role in linking the porphyrin centered 1ππ* and 3ππ* configurations. A simple model is presented that allows a rapid evolution between these two configurations, via coupling with the free d electron on the copper, getting around the spin orbit coupling in the porphyrin π.
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Han, D., Nave, S., & Jackson, B. (2013). Dissociative chemisorption of methane on Pt(110)-(1x2): effects of lattice motion on reactions at step edges. J Phys Chem A, 117(36), 8651–8659.
Résumé: The dissociative chemisorption of methane on Pt(110)-(1x2) is examined, with a focus on how the reaction dynamics are modified by the motion of the lattice atoms. The barriers to dissociation are found to be lowest at the step edges. The relaxation of the lattice in the presence of the dissociating molecule is found to be far more complicated than on the smooth surfaces of Pt and Ni. The dissociative sticking probabilities are computed using a full-dimensional treatment based on the reaction path Hamiltonian that includes all 15 molecular degrees of freedom and the effects of lattice motion. The potential energy surface and all parameters in our model are computed from first principles. The effects of lattice motion are strong, but not significantly larger than for dissociation on smoother surfaces. Vibrational excitation of the molecule can significantly enhance reactivity, though this effect varies from mode to mode. Agreement with recent experiments with regard to the variation of reactivity with translational energy and substrate temperature is good.
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Hartmann, J. - M., Boulet, C., Vieillard, T., Chaussard, F., Billard, F., Faucher, O., & Lavorel, B. (2013). Dissipation of alignment in CO2 gas: A comparison between ab initio predictions and experiments. JOURNAL OF CHEMICAL PHYSICS, 139(2), 024306.
Résumé: We present comparisons between measurements and ab initio calculations of the dissipation of the nonadiabatic laser-induced alignment in pure CO2 and CO2-He gas mixtures. The experiments were made for pressures between 2 and 20 bars at 295 K by using short non-resonant linearly polarized laser pulses for alignment and probe. The calculations are carried, free of any adjusted parameter, using refined intermolecular potentials and a requantized Classical Molecular Dynamics Simulations approach presented previously but not yet confronted to experiments. The results demonstrate that the model accurately reproduces the decays with time of both the transient revivals and “permanent” component of the alignment. The significant differences observed between the behaviors resulting from CO2-CO2 and CO2-He collisions are also well predicted by the model. (C) 2013 AIP Publishing LLC.
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Hartmann, J. - M., Sironneau, V., Boulet, C., Svensson, T., Hodges, J. T., & Xu, C. T. (2013). Collisional broadening and spectral shapes of absorption lines of free and nanopore-confined O-2 gas. PHYSICAL REVIEW A, 87(3), 032510.
Résumé: This paper presents fully ab initio calculations of the broadenings and spectral shapes of O-2 infrared absorption lines in a free gas and when confined in nanoporous media. These calculations are performed, without use of any adjusted parameter, using a recently proposed approach [Phys. Rev. A 87, 013403 (2013)] that is based on requantized classical molecular-dynamics simulations. This involves studying the time evolutions of the translational and rotational motions of large numbers of molecules taking molecule-molecule and molecule-surface collisions into account through realistic interaction potentials. These simulations enable predictions of dipole autocorrelation functions whose Fourier-Laplace transforms yield the associated spectra. Comparisons are then made with broadening coefficients and line shapes provided by new and previous experiments. The good agreement between calculated and measured results confirms the veracity of the proposed model for a free gas and shows that the effects of confinement, which induce significant modifications to the line shapes, are correctly predicted. The need for improved characterization of the shape and size of pores in random nanoporous media is highlighted. DOI: 10.1103/PhysRevA.87.032510
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Hoendervanger, A. L., Clement, D., Aspect, A., Westbrook, C. I., Dowek, D., Picard, Y. J., & Boiron, D. (2013). Influence of gold coating and interplate voltage on the performance of chevron micro-channel plates for temporally and spatially resolved single particle detection. REVIEW OF SCIENTIFIC INSTRUMENTS, 84(2), 023307.
Résumé: We present a study of two different sets of Micro-Channel Plates used for time and space resolved single particle detection. We investigate the effects of the gold coating and that of introducing an interplate voltage between the spatially separated plates. We find that the gold coating increases the count rate of the detector and the pulse amplitude as previously reported for non-spatially resolved setups. The interplate voltage also increases count rates. In addition, we find that a non-zero interplate voltage improves the spatial accuracy in determining the arrival position of incoming single particles (by ~20%) while the gold coating has a negative effect (by ~30%).
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Houplin, J., Amiaud, L., Humblot, V., Martin, I., Matar, E., Azria, R., Pradier, C. M., & Lafosse, A. (2013). Selective terminal function modification of SAMs driven by low-energy electrons (0-15 eV). Phys. Chem. Chem. Phys., 15(19), 7220–7227.
Résumé: Low-energy electron induced degradation of a model self-assembled monolayer (SAM) of acid terminated alkanethiol was studied under ultra-high vacuum (UHV) conditions at room and low (similar to 40 K) temperatures. Low-energy electron induced chemical modifications of 11-mercaptoundecanoic acid (MUA, HS-(CH2)(10)-COOH) SAMs deposited on gold were probed in situ as a function of the irradiation energy (<11 eV) by combining two complementary techniques: High Resolution Electron Energy Loss Spectroscopy (HREELS), a surface sensitive vibrational spectroscopy technique, and Electron Stimulated Desorption (ESD) analysis of neutral fragments. The SAM's terminal functions were observed to be selectively damaged at around 1 eV by a resonant electron attachment mechanism, observed to decay by CO, CO2 and H2O formation and desorption. CO2 and H2O were also directly identified at low temperature by vibrational analysis of the irradiated SAMs. At higher irradiation energy, both terminal functions and spacer alkyl chains are damaged upon electron irradiation, by resonant and non-resonant processes.
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Coherent Raman spectro-imaging with laser frequency combs. Nature, 502(7471), 355–8.
Résumé: Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques.
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Jackson, B., & Nave, S. (2013). The dissociative chemisorption of methane on Ni(111): The effects of molecular vibration and lattice motion. JOURNAL OF CHEMICAL PHYSICS, 138(17), 174705.
Résumé: We examine the dissociative chemisorption of methane on a Ni(111) surface, using a fully quantum approach based on the Reaction Path Hamiltonian that includes all 15 molecular degrees of freedom and the effects of lattice motion. The potential energy surface and all parameters in our model are computed from first principles. Vibrational excitation of the molecule is shown to significantly enhance the reaction probability, and the efficacy for this is explained in terms of the vibrationally non-adiabatic couplings, vibrational mode softening, and mode symmetry. Agreement with experimental data for molecules initially in the ground and 1nu3 state is good, and including lattice anharmonicity further improves our results. The variation of the dissociation probability with substrate temperature is well reproduced by the model, and is shown to result primarily from changes in the dissociation barrier height with lattice motion. The enhancement of dissociative sticking with substrate temperature is particularly strong for processes that would otherwise have insufficient energy to surmount the barrier. Our model suggests that vibrationally excited molecules are likely to dominate the “laser off” dissociative sticking at high nozzle temperatures.
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Jaouadi, A., Desouter-Lecomte M., Lefebvre, R., & Atabek, O. (2013). Signature of exceptional points in the laser control of non-adiabatic vibrational transfer. J. Phys. B: At. Mol. Opt. Phys., 46, 145402.
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Jaouadi, A., Desouter-Lecomte, M., Lefebvre, R., & Atabek, O. (2013). Exceptional points for logic operations at the molecular level. Fortschritte der Physik, 61, 162.
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Jia, J., Bendounan, A., Harish M.N.K., Chaouchi, K., Sirotti, F., Sampath, S., & and Esaulov V.A. (2013). Selenium Adsorption on Au(111) and Ag(111) Surfaces: Adsorbed Selenium and Selenide Films. JPhys Chem C, 117(19), 9835–9842.
Résumé: Results of a high resolution photoemission and electrochemistry study of Se adsorption on Au(111) and Ag(111) surfaces performed by immersion of pristine samples into an aqeuous solution of Na2Se are presented. Cyclic voltammetry on Au shows formation of selenium adsorbed species and the structures observed in reductive desorption are related to the atomic and polymeric species observed in XPS. In the case of Au(111) XPS spectra in the Se(3d) region indeed show two main features attributed to Se chemisorbed atomically and polymeric Se8 features. Smaller structures due to other types of Se conformations were also observed. The Au(4f) peak line shape does not show core level shifts indicative of Au selenide formation. In the case of silver, XPS spectra for the Ag(3d) show a broadening of the peak and a deconvolution into AgB bulk like and AgSe components shows that the AgSe is located at a lower binding energy, an effect similar to oxidation and sulfidation of Ag. The Se(3d) XPS spectrum is found to be substantially different from the Au case and dominated by atomic type Se due to the selenide, though a smaller intensity Se structure at an energy similar to the Se8 structure for Au is also observed. Changes in the valence band region related to Se adsorption are reported.
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Jia, J., Mukherjee, S., Hamoudi, H., Nannarone, S., Pasquali, L., & Esaulov, V. A. (2013). Lying-Down to Standing-Up Transitions in Self Assembly of Butanedithiol Monolayers on Gold and Substitutional Assembly by Octanethiols. J. Phys. Chem. C, 117(9), 4625–4631.
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Kokoouline, V., Wearne, A., Lefebvre, R., & Atabek, O. (2013). Laser-controlled rotational cooling of Na2 based on exceptional points. PHYSICAL REVIEW A, 88, 033408.
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Koval, N. E., Sánchez-Portal, D., Borisov, A. G., & Díez Muiño, R. (2013). Dynamic screening and energy loss of antiprotons colliding with excited Al clusters. Nucl. Instrum. Methods Phys. Res., B, 317, 56–60.
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Labidi, H., Sonnet, P., & Riedel, D. (2013). Electronic Control of the Tip-Induced Hopping of an Hexaphenyl-Benzene Molecule Physisorbed on a Bare Si(100) Surface at 9 K. JOURNAL OF PHYSICAL CHEMISTRY C, 117(26), 13663–13675.
Résumé: In this work, we show that the hopping directivity of individual hexaphenyl-benzene (HPB) molecules physisorbed along the SA step edge of a bare Si(100)-2×1 surface can be reversibly controlled with a periodic hopping length. This is achieved by using the tunnel electrons of a low temperature (9 K) scanning tunneling microscope (STM). A statistical analysis of the electronic excitations applied at various positions on the HPB molecule reveals that the hopping process is related to a strong decrease of the tunnel junction conductance. This process is associated with a charge transfer from the silicon surface to the HPB molecule leading to a hopping mechanism that occurs in two sequential steps. The first step of the hopping process involves the formation of an HPB− anion that triggers the molecular motion into a metastable state. The second step is related to the neutralization of the HPB− anion which provokes the manipulation of the molecule to its final steady position. Our experimental data are supported by the calculations of the relaxed molecule using the density functional theory on the Si(100) surface that takes the van der Waals forces interactions into account. Additional calculations of the HPB− anion orbitals depict the spatial localization of the extra charge inside the HPB molecule and the relative energies of the HPB− molecular orbitals. Finally, our study shows that the hopping direction can be optimized by positioning the STM tip at specific locations along the hopping pathway.
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Larroche, O., & Klisnick, A. (2013). Two-dimensional Maxwell-Bloch simulation of quasi-π-pulse amplification in a seeded XUV laser. Phys. Rev. A, 88(3), 033815.
Résumé: The amplification of high-order-harmonics (HOH) seed pulses in a swept-gain XUV laser is investigated through numerical simulations of the full set of Bloch and two-dimensional paraxial propagation equations with our code colax. The needed atomic data are taken from a hydrodynamics and collisional-radiative simulation in the case of a Ni-like Ag plasma created from the interaction of an infrared laser with a solid target and pumped in the transient regime. We show that the interplay of strong population inversion and diffraction or refraction due to the short transverse dimensions and steep density gradient of the active plasma can lead to the amplification of an intense, ultrashort, quasi-“π” pulse triggered by the incoming seed. By properly tuning the system geometry and HOH pulse parameters, we show that an ≃10 fs, 8×1012 W/cm2 amplified pulse can be achieved in a 3-mm-long Ni-like Ag plasma, with a factor of ≳10 intensity contrast with respect to the longer-lasting wake radiation and amplified spontaneous emission.
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Larroche, O., Meng, L., Le Marec, A., & Klisnick, A. (2013). Inversion density threshold for Rabi oscillations and modified small-signal gain in extreme-ultraviolet lasers. OPTICS LETTERS, 38(14), 2505–2508.
Résumé: An expression is proposed for a threshold discriminating between classical quasi-steady-state amplification and a strong pumping regime where a new dynamic behavior shows up in plasma-based extreme-ultraviolet (XUV) lasers. The criterion derived is applied to laser systems currently investigated in various laboratories. It is found that only high-gain XUV laser systems can be driven in that dynamic regime, associated with Rabi oscillations. For those systems, the small-signal dynamic gain accounting for the exponential amplification of the laser intensity is shown to be significantly smaller than the adiabatic value usually inferred from numerical simulations. (C) 2013 Optical Society of America
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Le Moal, E., Marguet, S., Rogez, B., Mukherjee, S., Dos Santos, P., Boer-Duchemin, E., Comtet, G., & Dujardin, G. (2013). An electrically excited nanoscale light source with active angular control of the emitted light. Nano Lett., 13(9), 4198–4205.
Résumé: The angular distribution, polarization, and spectrum of the light emitted from an electrically controlled nanoscale light source arises from the local, low-energy, electrical excitation of localized surface plasmons (LSP) on individual gold nanoparticles induced by a scanning tunneling microscope (STM). The gold nanoparticles (NP) are chemically synthesized truncated bitetrahedrons. The emitted light is collected through the transparent substrate The angular distribution, polarization, and spectrum are found to strongly depend on the lateral position of the STM tip with respect to the upper triangular face of the gold NP. The resulting light emission changes orientation when the electrical excitation via the STM tip is moved from the base to the vertex of the triangular face. Comparison with an analytical dipole model and finite-difference time-domain (FDTD) calculations shows that this behavior is linked to the selective excitation of the out-of-plane and in-plane dipolar LSP modes of the NP.
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Le Moal, S., Moors, M., Essen, J. M., Breinlich, C., Becker, C., & Wandelt, K. (2013). Structural and compositional characterization of ultrathin titanium oxide films grown on Pt3Ti(111). JOURNAL OF PHYSICS-CONDENSED MATTER, 25, 045013.
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Lefebvre, C., Nguyen-Dang, T. T., Dion, F., Vrakking, M. J. J., Serov, V. N., & Atabek, O. (2013). Attosecond pump-probe transition-state spectroscopy of laser-induced molecular dissociative ionization: Adiabatic versus nonadiabatic dressed-state dynamics. PHYSICAL REVIEW A, 88(5), 053416.
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Lefebvre, R., & Atabek, O. (2013). Dissociation quenching using exceptional points. Journal of Molecular Modeling, 19, 1959.
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Ma, Q., Boulet, C., & Tipping, R. H. (2013). Refinement of the Robert-Bonamy formalism: Considering effects from the line coupling. JOURNAL OF CHEMICAL PHYSICS, 139(3), 034305.
Résumé: Since it was developed in 1979, the Robert-Bonamy (RB) formalism has been widely used in calculating pressure broadened half-widths and induced shifts for many molecular systems. However, this formalism contains several approximations whose applicability has not been thoroughly justified. One of them is that lines of interest are well isolated. When these authors developed the formalism, they have relied on this assumption twice. First, in calculating the spectral density F(omega), they have only considered the diagonal matrix elements of the relaxation operator. Due to this simplification, effects from the line mixing are ignored. Second, when they applied the linked cluster theorem to remove the cutoff, they have assumed the matrix elements of the operator exp(-iS(1) – S-2) can be replaced by the exponential of the matrix elements of -iS(1) – S-2. With this replacement, effects from the line coupling are also ignored. Although both these two simplifications relied on the same approximation, their validity criteria are completely different and the latter is more stringent than the former. As a result, in many cases where the line mixing becomes negligible, significant effects from the line coupling have been completely missed. In the present study, we have developed a new method to evaluate the matrix elements of exp(-iS(1) – S-2) and have refined the RB formalism such that line coupling can be taken into account. Our numerical calculations of the half-widths for Raman Q lines of the N-2-N-2 pair have demonstrated that effects from the line coupling are important. In comparison with values derived from the RB formalism, new calculated values for these lines are significantly reduced. A recent study has shown that in comparison with the measurements and the most accurate close coupling calculations, the RB formalism overestimates the half-widths by a large amount. As a result, the refinement of the RB formalism goes in the right direction and these new calculated half-widths become closer to the “true” values. (C) 2013 AIP Publishing LLC.
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Mahjoub, A., Le Barbu-Debus, K., & Zehnacker, A. (2013). Structural Rearrangement in the Formation of Jet-Cooled Complexes of Chiral (S)-1,2,3,4-Tetrahydro-3-isoquinolinemethanol with Methyl Lactate: Chirality Effect in Conformer Selection. JOURNAL OF PHYSICAL CHEMISTRY A, 117(14), 2952–60.
Résumé: The jet-cooled complexes between the two enantiomers of methyl lactate (ML) and (S)-1,2,3,4-tetrahydro-3-isoquinolinemethanol (THIQM) are studied by double resonance spectroscopy combined with ab initio calculations. Both diastereomer complexes exist in different isomers, involving either direct addition of THIQM on ML with no structural rearrangement of the subunits or formation of very stable structures involving multiple intermolecular hydrogen bonds and extensive deformation of the subunits. Competition between these two processes and its dependence upon chirality are discussed. It is shown that the most stable form of the chromophore (THIQMI with an OH···N hydrogen bond) prefers to directly stick to ML to form the addition complex whereas the second conformer (THIQMII with NH···O hydrogen bond) rearranges to form a strongly bound structure. The two structures are formed for the homochiral as well the heterochiral complex, however with different relative abundance. This shows an enantioselective binding preference of ML for one of the conformers of the chromophore.
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Majzik, Z., Tchalala, M. R., Svec, M., Hapala, P., Enriquez, H., Kara, A., Mayne, A. J., Dujardin, G., Jelinek, P., & Oughaddou, H. (2013). Combined AFM and STM measurements of a silicene sheet grown on the Ag(111) surface. JOURNAL OF PHYSICS-CONDENSED MATTER, 25(22), 225301.
Résumé: In this paper, we present the first non-contact atomic force microscopy (nc-AFM) of a silicene on a silver (Ag) surface, obtained by combining non-contact atomic force microscopy and scanning tunneling microscopy (STM). STM images over large areas of silicene grown on the Ag(111) surface show both (root 13 x root 13)R13.9 and (4 x 4) superstructures. For the widelyobserved (4 x 4) structure, the observed nc-AFM image is very similar to the one recorded by STM. The structure resolved by nc-AFM is compatible with only one out of two silicon atoms being visible. This indicates unambiguously a strong buckling of the silicene honeycomb layer.
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Makarov, D. S., Tretyakov, M. Y., & Boulet, C. (2013). Line mixing in the 60-GHz atmospheric oxygen band: Comparison of the MPM and ECS model. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 124, 1–10.
Résumé: Precise profiles of the 60-GHz molecular oxygen band recorded earlier in a wide temperature range by means of a resonator spectrometer at atmospheric pressure were treated. High signal-to-noise ratio allows careful study of the band shape taking into consideration the mixing effect. Comparative analysis of the band profile calculated by an extended MPM (Millimeter-wave Propagation Model) and by the ECS (Energy Corrected Sudden) approximation model is presented. Some limitations of the MPM approach are discussed on the basis of the comparison of the two models. Interbranch coupling is shown to make a noticeable contribution to absorption which means that it should be taken into account as it is expected to improve band profile modeling accuracy. (c) 2013 Elsevier Ltd. All rights reserved.
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Marggi Poullain, S., Veyrinas, K., Billaud, P., Lebech, M., Picard, Y. J., Lucchese, R. R., & Dowek, D. (2013). The role of Rydberg states in photoionization of NO2 and (NO+, O-) ion pair formation induced by one VUV photon. JOURNAL OF CHEMICAL PHYSICS, 139(4), 044311.
Résumé: We report a combined experimental and theoretical study of photoionization (PI) of the NO2 molecule into the NO2+ (X-1 Sigma(+)(g)) ground state and the photodissociation of NO2 into the NO+((1)Sigma(+)) + O-(P-2) ion pair. These processes were induced by 10.9 eV-13 eV synchrotron radiation and the products were detected using electron-ion or O--NO+ coincident momentum spectroscopy. The results demonstrate the strong influence of [R*(4b(2))(-1), nl alpha(i), v'(2)] Rydberg states vibrationally resolved in the v'(2) bending modes for both processes. In particular, we emphasize two regions around 11.5 eV and 12.5 eV that were studied in more detail for their relevance to 400 nm multiphoton ionization induced by femtosecond pulses. The photoelectron energy spectra and asymmetry parameters support the existence of two PI mechanisms, as probed with the help of fixed-nuclei frozen-core Hartree-Fock calculations. We found significant deviations from Franck-Condon ionization predictions which may be assigned to vibronic coupling of NO2* states such as that induced by a conical intersection. The limited agreement between theory and experiment, even for the non-resonant processes, indicates the need for calculations that go beyond the approximations used in the current study. Ion pair formation leads to strong vibrational and rotational excitation of the NO+((1)Sigma(+), v) product, with an ion fragment angular anisotropy depending on both the v'(2) bending quantum number of the excited parent molecule and the v vibrational level of the fragment. (C) 2013 AIP Publishing LLC.
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Marinica, D. C., Lourenco-Martins, H., Aizpurua, J., & Borisov, A. G. (2013). Plexciton quenching by resonant electron transfer from quantum emitter to metallic nanoantenna. Nano Lett., 13(12), 5972–5978.
Résumé: Coupling molecular excitons and localized surface plasmons in hybrid nanostructures leads to appealing, tunable optical properties. In this respect, the knowledge about the excitation dynamics of a quantum emitter close to a plasmonic nanoantenna is of importance from fundamental and practical points of view. We address here the effect of the excited electron tunneling from the emitter into a metallic nanoparticle(s) in the optical response. When close to a plasmonic nanoparticle, the excited state localized on a quantum emitter becomes short-lived because of the electronic coupling with metal conduction band states. We show that as a consequence, the characteristic features associated with the quantum emitter disappear from the optical absorption spectrum. Thus, for the hybrid nanostructure studied here and comprising quantum emitter in the narrow gap of a plasmonic dimer nanoantenna, the quantum tunneling might quench the plexcitonic states. Under certain conditions the optical response of the system approaches that of the individual plasmonic dimer. Excitation decay via resonant electron transfer can play an important role in many situations of interest such as in surface-enhanced spectroscopies, photovoltaics, catalysis, or quantum information, among others.
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Martin-Drumel, M. A., Pirali, O., Loquais, Y., Falvo, C., & Brechignac, P. (2013). Lowest energy vibrational modes of some naphthalene derivatives: Azulene, quinoline, isoquinoline – Experiment and theory. CHEMICAL PHYSICS LETTERS, 557, 53–58.
Résumé: Far infrared (FIR) gas phase absorption spectra of azulene, quinoline and isoquinoline have been recorded using a Fourier transform Bruker IFS125 interferometer at medium resolution (0.5 cm(-1)). Assignments of these weak vibrational bands were performed using density-functional theory calculations carried out at the harmonic and anharmonic levels. Agreement between observed and calculated band positions is better than 5% for azulene and 1% for quinoline and isoquinoline. The relative band intensities are also correctly predicted. Molecular structure dependence of the FIR spectra is discussed based on the comparative study of three selected FIR modes. (C) 2012 Elsevier B.V. All rights reserved.
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Miyazaki, M., Kawanishi, A., Nielsen, I., Alata, I., Ishiuchi, S. -ichi, Dedonder, C., Jouvet, C., & Fujii, M. (2013). Ground state proton transfer in phenol-(NH3)(n) (n </= 11) clusters studied by mid-IR spectroscopy in 3-10 mum range. J Phys Chem A, 117(7), 1522–1530.
Résumé: The infrared (IR) spectra of size-selected phenol-ammonia clusters, PhOH-(NH(3))(n) (n </= 11) in the 3-10 mum wavelength region were measured to investigate the critical number of solvent molecules necessary to promote the ground state proton transfer (GSPT) reaction. While the N-H stretching vibrations did not provide clear information, characteristic changes that are assigned to the GSPT reaction were observed in the skeletal vibrational region. The production of phenolate anion (PhO(-)), which is a product of the GSPT reaction, was established from the appearance of characteristic bands assignable to C-C stretching and C-H bending vibrations of PhO(-) and from the corresponding disappearance of C-O-H bending vibration of PhOH at n = 9. The mid-IR spectroscopy directly proves the structural change induced by the deprotonation from the O-H bond and thus establishes the GSPT reaction as complete at n = 9. No such absorptions were observed for n </= 5 in line with a previous report. For n = 6-8, both the proton transferred and the nontransferred signatures were observed in the spectra, showing coexistence of both species for the first time.
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O'Keeffe, P., Gryzlova, E. V., Cubaynes, D., Garcia, G. A., Nahon, L., Grum-Grzhimailo, A. N., & Meyer, M. (2013). Isotopically Resolved Photoelectron Imaging Unravels Complex Atomic Autoionization Dynamics by Two-Color Resonant Ionization. PHYSICAL REVIEW LETTERS, 111(24), 243002.
Résumé: Angle-resolved electron spectroscopy in coincidence with high-resolution mass spectroscopy has been applied to study two-color resonant photoionization in atomic xenon. Separation of different isotopes enabled us to extract results for the electronic dynamics free from depolarization effects, which are generally introduced by the coupling of the electronic and nuclear angular momenta. The concerted experimental and theoretical analysis of the photoelectron angular distributions in the region of an autoionizing resonance emphasizes the strong sensitivity of the observed structures to the fine details of the treatment of the underlying dynamics.
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Oh, E., Fatemi, F. K., Currie, M., Delehanty, J. B., Pons, T., Fragola, A., Lévêque-Fort, S., Goswami, R., Susumu, K., Huston, A. L., & Medintz, I. L. (2013). PEGylated Luminescent Gold Nanoclusters: Synthesis, Characterization, Bioconjugation, and Application to One- and Two-Photon Cellular Imaging. Part. Part. Syst. Charact., 30(5), 453–466.
Résumé: Biocompatible, near-infrared luminescent gold nanoclusters (AuNCs) are synthesized directly in water using poly(ethylene glycol)-dithiolane ligands terminating in either a carboxyl, amine, azide, or methoxy group. The ≈1.5 nm diameter AuNCs fluoresce at ≈820 nm with quantum yields that range from 4–8%, depending on the terminal functional group present, and display average luminescence lifetimes approaching 1.5 μs. The two-photon absorption (TPA) cross-section and two-photon excited fluorescence (TPEF) properties are also measured. Long-term testing shows the poly(ethylene glycol) stabilized AuNCs maintain colloidal stability in a variety of media ranging from saline to tissue culture growth medium along with tolerating storage of up to 2 years. DNA and dye-conjugation reactions confirm that the carboxyl, amine, and azide groups can be utilized on the AuNCs for carbodiimide, succinimidyl ester, and CuI-assisted cycloaddition chemistry, respectively. High signal-to-noise one- and two-photon cellular imaging is demonstrated. The AuNCs exhibit outstanding photophysical stability during continuous-extended imaging. Concomitant cellular viability testing shows that the AuNCs also elicit minimal cytotoxicity. Further biological applications for these luminescent nanoclustered materials are discussed.
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Orieux, A., Eckstein, A., Lemaître, A., Filloux, P., Favero, I., Leo, G., Coudreau, T., Keller, A., Milman, P., & Ducci, S. (2013). Direct Bell States Generation on a III-V Semiconductor Chip at Room Temperature. PRL, 110(16), 160502.
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Orthous-Daunay, F. R., Quirico, E., Beck, P., Brissaud, O., Dartois, E., Pino, T., & Schmitt, B. (2013). Mid-infrared study of the molecular structure variability of insoluble organic matter from primitive chondrites. ICARUS, 223(1), 534–543.
Résumé: Insoluble Organic Matter (IOM) found in primitive meteorites was formed in the Early Solar System and subsequently processed on the parent asteroids. The location, temporal sequence and processes of formation of this IOM are still a matter of debate. In particular, there is no consensus on the actual effect of post-accretional aqueous alteration processes on the chemical composition and structure of IOM. In the most primitive chondrites (types I and 2), these alterations have so far been either neglected or generically assigned to oxidation processes induced by fluid circulation. A series of IOM samples extracted from 14 chondrites with extensively documented post-accretional histories have been studied by infrared spectroscopy. Aqueous alteration shows no detectable effect on the chemical composition and structure of IOM within or across chondrite classes. Indeed, the most effective post-accretional process appears to be a high-temperature short-duration heating event and concerns essentially type 2 chondrites. In any case, post-accretional processes cannot account for all the chemical and structural variations of IOM. Chondrites from the CI, CR and CM classes accreted IOM precursors with moderately variable compositions, suggesting a chemical heterogeneity of the protosolar disk. The 3.4 μm band, and possibly its overtones and combinations in the near-infrared range, appear to be tracer(s) of the chemical class and possibly of surface heating processes triggered by impacts. (C) 2013 Elsevier Inc. All rights reserved.
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Ovramenko, T., Spillebout, F., Bocquet, F. C., Mayne, A. J., Dujardin, G., Sonnet, P., Stauffer, L., Ksari, Y., & Themlin, J. M. (2013). STM imagery and density functional calculations of C-60 fullerene adsorption on the 6H-SiC(0001)-3x3 surface. Phys. Rev. B, 87(15), 155421.
Résumé: Scanning tunneling microscopy (STM) studies of the fullerene C-60 molecule adsorbed on the silicon carbide SiC(0001)-3 x 3 surface, combined with density functional theory (DFT) calculations, show that chemisorption of individual C-60 molecules occurs through the formation of one bond to one silicon adatom only in contrast to multiple bond formation on other semiconducting surfaces. We observe three stable adsorption sites with respect to the Si adatoms of the surface unit cell. Comprehensive DFT calculations give different adsorption energies for the three most abundant sites showing that van der Waals forces between the C-60 molecule and the neighboring surface atoms need to be considered. The C-60 molecules are observed to form small clusters even at low coverage indicating the presence of a mobile molecular precursor state and nonnegligible intermolecular interactions. DOI: 10.1103/PhysRevB.87.155421
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O’Rourke, B. E., Flores, M., Esaulov, V. A., & Yamazaki, Y. (2013). Modification of self assembled monolayers by highly charged ions. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and , 299, 68–70.
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Parneix P., Basire M., & Calvo F. (2013). Accurate Modeling of Infrared Multiple Photon Dissociation Spectra: The Dynamical Role of Anharmonicities. JOURNAL OF PHYSICAL CHEMISTRY A, 117(19), 3954–3959.
Résumé: The dynamical response of a molecular system to a macropulse typically produced by a free-electron laser is theoretically modeled over experimentally long times, within a realistic kinetic Monte Carlo framework that incorporates absorption, stimulated emission, spontaneous emission, and dissociation events. The simulation relies on an anharmonic potential energy surface obtained from quantum chemistry calculations. Application to cationic naphthalene yields a better agreement with measurements than the anharmonic linear absorption spectrum, thus emphasizing the importance of specific dynamical effects on the spectral properties.
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Pirali O., Goubet M., Huet T.R., Georges R., Soulard P., Asselin P., Courbe J., Roy P., & & Vervloet M. (2013). The far infrared spectrum of naphthalene characterized by high resolution synchrotron FTIR spectroscopy and anharmonic DFT calculations. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10141–10150.
Résumé: Using synchrotron radiation, we performed the rotationally resolved Fourier transform infrared absorption spectroscopy of three bands of naphthalene C10H8, namely ν46-0 (centered at 782 cm−1, 12.7 μm), ν47-0 (centered at 474 cm−1, 21 μm), and ν48-0 (centered at 167 cm−1, 60 μm). The intense CH bending out of plane ν46-0 band was recorded under supersonic jet-cooled conditions using a molecular beam (the Jet-AILES apparatus) and the low frequency ν47-0 and ν48-0 bands were measured at room temperature in a long absorption path cell. The simultaneous rotational analysis of these bands permitted us to refine the ground state (GS) and ν46 rotational spectroscopic constants and to provide the first sets of constants for the ν47 and ν48 modes. The experimental rotational constants were then used as reference data to calibrate theoretical models in order to provide new insights into the accuracy of anharmonic calculations. The B97-1 functional associated with the cc-pVTZ and ANO-RCC basis sets gave a consistent set of results, for rotational constants and fundamental frequencies. The data presented here pave the way for the search of naphthalene through its far-infrared spectrum in different objects of the interstellar medium.
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Raseev, G. (2013). Plasmon resonances of Ag(001) and Ag(111) studied by power density absorption and photoyield. Surf. Sci., 615, 6–20.
Résumé: This paper models the surface and bulk plasmon resonances in photoabsorption and photoelectron spectra (PES) of the Ag(001) and the Ag(111) surfaces in the region of 2.8-10 eV excited with a p or transverse magnetic linearly polarized laser incident at 45 degrees. Using the recently developed vector potential from electron density-coupled integro-differential equations (VPED-CIDE, [1,2]) model, we calculate the electron escaping probability from the power density absorption, Feibelman's parameter d(perpendicular to), the reflectance and the Fermi PE cross section. In the PES experiment the work function is lowered from 45 to 2.8 eV by adsorption of sodium. In our model, this lowering is introduced by adding a phenomenological term to the DFT-LDA model potential of Chulkov et al. [3]. For both Ag(001) and Ag(111), the calculated observables display two plasmon resonances, the multipole surface at 3.70 eV and the bulk at 3.90 eV, in fair agreement with the experimental PES of Barman et al. [4,5] and the reflectance. Except for the Fermi PE cross section of Ag(001) which does not display the multipole surface plasmon resonance at 3.70 eV. This poor result is probably due to a poor calculation of the conduction band wave functions obtained from the Schrodinger equation using the modified DFT-LDA model potential of Chulkov et at (C) 2013 Elsevier B.V. All rights reserved.
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Rios Rubiano, C. A., Bocan, G. A., Gravielle, M. S., Bundaleski, N., Khemliche, H., & Roncin, P. (2013). Ab initio potential for the He-Ag(110) interaction investigated using grazing-incidence fast-atom diffraction. Phys. Rev. B, 87(1), 012903.
Résumé: Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test an ab initio potential model derived from accurate density-functional theory (DFT) calculations. The scattering process is described by means of the surface eikonal approximation, which is a distorted-wave method that includes the quantum interference between contributions coming from different projectile paths, taking into account the complete corrugation of the three-dimensional projectile-surface potential. A fairly good agreement between the theoretical and experimental momentum distributions is found for incidence along different low-indexed crystallographic directions. This agreement is indicative of the quality of the DFT potential. The effective corrugation of the interaction potential across the incidence channel is also investigated. DOI: 10.1103/PhysRevA.87.012903
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Salazar Alarcón, L., Cristina, L. J., Shen, J., Jia, J., Esaulov, V. A., Sánchez, E. A., & Grizzi, O. (2013). Growth of 1,4-Benzenedimethanethiol Films on Au, Ag, and Cu: Effect of Surface Temperature on the Adsorption Kinetics and on the Single versus Multilayer Formation. J. Phys. Chem. C, 117(34), 17521–17530.
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Sarsa, A., Alcaraz-Pelegrina, J. M., Le Sech, C., & Cruz, S. A. (2013). Quantum Confinement of the Covalent Bond beyond the Born-Oppenheimer Approximation. Journal Of Physical Chemistry B, 117(24), 7270–7276.
Résumé: Dirichlet boundary conditions with different symmetries, spherical and cylindrical impenetrable surfaces, are imposed on the covalent electron pair of a molecular bond. Accurate results for different observable like energy and interparticle distances are calculated using quantum Monte Carlo methods beyond the Born-Oppenheimer approximation. The spherical confinement induces a raise in the bond energy and shortens the internuclear distances even for a relatively soft confinement. When cylindrical symmetry is considered, similar qualitative behavior is observed though only the electrons are confined. A compression followed by a relaxation process of the confined bond is shown to induce a vibrationally excited state. Finally, a brief qualitative discussion based on a simplified picture of the role of compression/relaxation cycles in enzyme catalysis is given.
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Schaffert, J., Cottin, M. C., Sonntag, A., Bobisch, C. A., Moeller, R., Gauyacq, J. - P., & Lorente, N. (2013). Tunneling electron induced rotation of a copper phthalocyanine molecule on Cu(111). Phys. Rev. B, 88(7), 075410.
Résumé: The rates of a hindered molecular rotation induced by tunneling electrons are evaluated using scattering theory within the sudden approximation. Our approach explains the excitation of copper phthalocyanine molecules (CuPc) on Cu(111) as revealed in a recent measurement of telegraph noise in a scanning tunneling microscopy experiment [Schaffert et al., Nat. Mater. 12, 223 (2013)]. A complete explanation of the experimental data is performed by computing the geometry of the adsorbed system, its electronic structure, and the energy transfer between tunneling electrons and the molecule's rotational degree of freedom. The results unambiguously show that tunneling electrons induce a frustrated rotation of the molecule. In addition, the theory determines the spatial distribution of the frustrated rotation excitation, confirming the striking dominance of two out of four molecular lobes in the observed excitation process. This lobe selectivity is attributed to the different hybridizations with the underlying substrate.
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Schaffert, J., Cottin, M. C., Sonntag, A., Karacuban, H., Bobisch, C. A., Lorente, N., Gauyacq, J. - P., & Möller, R. (2013). Imaging the dynamics of individually adsorbed molecules. Nat. Mater., 12(3), 223–227.
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Sebban, S., Zeitoun, P., & Klisnick, A. (2013). Breakthroughs in Photonics 2012: New Advances in Soft X-Ray Lasers and Applications. IEEE PHOTONICS JOURNAL, 5(2), 0700204.
Résumé: This paper reviews the major accomplishments in the development of plasma-based soft X-ray lasers and their applications in 2012. Significant experimental breakthroughs include the extension of the lasing range down to 1.5 nm in an X-FEL photoionized plasma and the 100-Hz operation of a 18.9-nm laser with a record average power of 0.15 mW. New fields of applications, exploiting the high-brightness, coherence, and compactness of the source, were demonstrated. Further breakthroughs toward higher peak power are anticipated from numerical simulations of injection-seeded soft X-ray lasers.
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Sen, A., Le Barbu-Debus, K., Scuderi, D., & Zehnacker-Rentien, A. (2013). Mass Spectrometry Study and Infrared Spectroscopy of the Complex Between Camphor and the Two Enantiomers of Protonated Alanine: The Role of Higher-Energy Conformers in the Enantioselectivity of the Dissociation Rate Constants. Chirality, 25, 436–443.
Résumé: The properties of the protonated complexes built from S camphor and R or S alanine were studied in a Paul ion trap at room temperature by collision-induced dissociation (CID) and infrared multiple-photon dissociation spectroscopy (IRMPD), as well as molecular dynamics and ab initio calculations. While the two diastereomer complexes display very similar vibrational spectra in the fingerprint region, in line with similar structures, and almost identical calculated binding energies, their collision-induced dissociation rates are different. Comparison of the IRMPD results to computed spectra shows that the SS and SR complexes both contain protonated alanine strongly hydrogen-bonded to the keto group of camphor. The floppiness of this structure around the NH+…O = C hydrogen bond results in a complex potential energy surface showing multiple minima. Calculating the dissociation rate constant within the frame of the transition state theory shows that the fragmentation rate larger for the heterochiral SR complex than the homochiral SS complex can be explained in terms of two almost isoenergetic low-energy conformers in the latter that are not present for the former. Chirality 00:000-000, 2013. © 2013 Wiley Periodicals, Inc.
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Sen, A., Lepere, V., Le Barbu-Debus, K., & Zehnacker, A. (2013). How do Pseudoenantiomers Structurally Differ in the Gas Phase? An IR/UV Spectroscopy Study of Jet-Cooled Hydroquinine and Hydroquinidine. CHEMPHYSCHEM, 14(15), 3559–3568.
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Shen, J., Jia, J., Bobrov, K., Guillemot, L., & Esaulov, V. A. (2013). Electron transfer processes on Au nanoclusters supported on graphite. Gold Bull, 46(4), 343–347.
Résumé: Electron transfer processes play an important role in surface chemistry. This paper presents results of a study of changes in resonant electron transfer processes, as a function of gold cluster sizes, on the example of electron transfer between Li+ ions scattered on Au clusters on highly oriented pyrolytic graphite (HOPG). The gold nanoclusters were grown on lightly sputtered HOPG surface in order to obtain a wide coverage distribution of clusters. The growth of clusters was monitored by scanning tunneling microscopy. We found that electron transfer is much more probable on small clusters, whose lateral size is of the order of 2 to 3 nm and height in the 1-nm range, than on bulk Au or thin Au films. A comparison with Au clusters grown on the semiconducting titania did not reveal significant differences with HOPG.
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Sitja, G., Le Moal, S., Marsault, M., Hamm, G., Leroy, F., & Henry, C. R. (2013). Transition from molecule to solid state : reactivity of supported metal clusters. NANO LETTERS, 13, 1977–1982.
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Song, J., Bouchoule, S., Patriarche, G., Galopin, E., Yacomotti, A. M., Cambril, E., Kou, Q., Troadec, D., He, J. - J., & Harmand, J. - C. (2013). Improvement of the oxidation interface in an AlGaAs/AlxOy waveguide structure by using a GaAs/AlAs superlattice. Physica Status Solidi A-Applications And Materials Science, 210(6), 1171–1177.
Résumé: The wet oxidation from the mesa sidewalls of AlGaAs/GaAs epitaxial structures is investigated in details. In addition to the intended lateral oxidation of the Al-rich buried layer, we observe a parasitic vertical oxidation of the adjacent layers of lower Al content. This vertical oxidation produces a rough interface between the oxidized and non-oxidized materials and reduces the effective thickness of the adjacent layers. This detrimental phenomenon is drastically reduced when the adjacent layer is replaced by a GaAs/AlAs superlattice (SL). In this case, a sharp interface between the Al-Ga-oxide and the SL is obtained after the oxidation process. Further experiments point out the critical role of hydrogen in the oxidation process of low Al content alloys. Hydrogen atoms produced during the oxidation of the Al-rich layer are proposed to be responsible for the vertical oxidation of the adjacent layers. We devise that the SL interfaces are favorable to reduce the diffusion of the reactants in the vertical direction.
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Stanca-Kaposta, E. C., Carcabal, P., Cocinero, E. J., Hurtado, P., & Simons, J. P. (2013). Carbohydrate-Aromatic Interactions: Vibrational Spectroscopy and Structural Assignment of Isolated Monosaccharide Complexes with p-Hydroxy Toluene and N-Acetyl L-Tyrosine Methylamide. J. Phys. Chem. B, 117(27), 8135–8142.
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Sugny, D., Vranckx, S., Ndong, M., Atabek, O., & Desouter-Lecomte, M. (2013). External constraints on optimal control strategies in molecular orientation and photofragmentation: role of zero-area fields. Journal of Modern Optics, 61, 816.
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Tchalala, M. R., Ali, M. A., Enriquez, H., Kara, A., Lachgar, A., Yagoubi, S., Foy, E., Vega, E., Bendounan, A., Silly, M. G., Sirotti, F., Nitshe, S., Chaudanson, D., Jamgotchian, H., Aufray, B., Mayne, A. J., Dujardin, G., & Oughaddou, H. (2013). Silicon sheets by redox assisted chemical exfoliation. JOURNAL OF PHYSICS-CONDENSED MATTER, 25(44), 442001.
Résumé: In this paper, we report the direct chemical synthesis of silicon sheets in gram-scale quantities by chemical exfoliation of pre-processed calcium disilicide (CaSi2). We have used a combination of x-ray photoelectron spectroscopy, transmission electron microscopy and energy-dispersive x-ray spectroscopy to characterize the obtained silicon sheets. We found that the clean and crystalline silicon sheets show a two-dimensional hexagonal graphitic structure.
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Tchalala, M. R., Enriquez, H., Mayne, A. J., Kara, A., Roth, S., Silly, M. G., Bendounan, A., Sirotti, F., Greber, T., Aufray, B., Dujardin, G., Ali, M. A., & Oughaddou, H. (2013). Formation of one-dimensional self-assembled silicon nanoribbons on Au(110)-(2 x 1). APPLIED PHYSICS LETTERS, 102(8), 083107.
Résumé: We report results on the self-assembly of silicon nanoribbons (NRs) on the (2 x 1) reconstructed Au(110) surface under ultra-high vacuum conditions. Upon adsorption of 0.2 monolayer (ML) of silicon, the (2 x 1) reconstruction of Au(110) is replaced by an ordered surface alloy. Above this coverage, a new superstructure is revealed by low energy electron diffraction (LEED), which becomes sharper at 0.3 Si ML. This superstructure corresponds to Si nanoribbons all oriented along the [(1) over bar 10] direction as revealed by LEED and scanning tunneling microscopy (STM). STM and high-resolution photoemission spectroscopy indicate that the nanoribbons are flat and predominantly 1.6 nm wide. In addition, the silicon atoms show signatures of two chemical environments corresponding to the edge and center of the ribbons. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793536]
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Teperik, T. V., Nordlander, P., Aizpurua, J., & Borisov, A. G. (2013). Quantum effects and nonlocality in strongly coupled plasmonic nanowire dimers. Opt. Express, 21(22), 27306.
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Teperik, T. V., Nordlander, P., Aizpurua, J., & Borisov, A. G. (2013). Robust Subnanometric Plasmon Ruler by Rescaling of the Nonlocal Optical Response. Phys. Rev. Lett., 110(26), 263901.
Résumé: We present the optical response of two interacting metallic nanowires calculated for separation distances down to angstrom range. State-of-the-art local and nonlocal approaches are compared with full quantum time-dependent density functional theory calculations that give an exact account of nonlocal and tunneling effects. We find that the quantum results are equivalent to those from classical approaches when the nanoparticle separation is defined as the separation between centroids of the screening charges. This establishes a universal plasmon ruler for subnanometric distances. Such a ruler not only impacts the basis of many applications of plasmonics, but also provides a robust rule for subnanometric metrology.
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Thon, R., Chin, W., Galaup, J. - P., Ouvrard, A., Bourguignon, B., & Crepin, C. (2013). Vibrational Perturbations of W(CO)(6) Trapped in a Molecular Lattice Probed by Linear and Nonlinear Spectroscopy. J. Phys. Chem. A, 117(34), 8145–8156.
Résumé: Vibrational dynamics of the T-1u CO stretching mode of tungsten hexacarbonyl is explored when the molecule is embedded in a nitrogen matrix at low temperature. Experiments combined infrared (IR) absorption spectroscopy and IR stimulated photon echoes at the femtosecond time scale. W(CO)(6) is found to be trapped in two main families of sites differing by their symmetry (called hereafter O-h and D-2h sites). In O-h sites, the vibrational coherence is strongly temperature dependent, exhibiting a coupling with librational phonons of the nitrogen lattice. Perturbation in D-2h sites results in the splitting of the T-1u band in three components. Each component is inhomogeneously broadened, with dephasing times in the tens of picoseconds, and is weakly coupled to the lattice phonons. Experiments in solid krypton are performed to compare the effect of atomic and diatomic host lattices. Dephasing time in Kr does not depend on temperature and remains in the hundreds of picoseconds, highlighting the molecular origin of the dephasing process in N-2. Additionally, nonlinear signals show oscillations due to quantum beats and polarization interferences between different frequency components of the induced third order polarization, giving information, in particular, on the overtone vibrational transition.
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Tsirkin, S. S., Borisov, A. G., & Chulkov, E. V. (2013). Green's function approach to the lifetimes of image potential resonances at metal surfaces. Phys. Rev. B, 88(3), 035449.
Résumé: We present a theoretical study of the image potential resonances (IPRs) at metal surfaces. We develop the Green's functions approach allowing us to calculate binding energies E-n and lifetimes tau(n) of IPRs with high quantum numbers n (up to 10 in this work). A systematic study is performed at the (Gamma) over bar point for the close-packed metal surfaces: Cu(111), Ag(111), Au(111), Al(001), Al(111), Be(0001), Mg(0001), Na(110), Li(110), and also at the (Y) over bar point on Cu(110). The calculated lifetimes of IPRs on close-packed surfaces demonstrate the scaling law tau(n) proportional to n(3). Our results are in agreement with available experimental data. We show that at the (Y) over bar point on Cu(110) each quantum number n corresponds to a pair of IPRs n(+) and n(-), where the energy difference En+ – En- is proportional to n(-3). The lifetimes tau(n+) and tau(n-) differ significantly, however, they both obey the scaling law tau(n +/-) proportional to n(3). Since the electrons trapped in the long-lived IPRs are strongly localized on the vacuum side, we argue that the inelastic electron-electron and electron-phonon scattering have a small contribution to the decay rate of these IPRs. The latter is dominated by the resonant electron transfer into the bulk.
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Tudorie, M., Kleiner, I., Jahn, M., Grabow, J. U., Goubet, M., & Pirali, O. (2013). Coupled Large Amplitude Motions: A Case Study of the Dimethylbenzaldehyde Isomers. Journal of Physical Chemistry A, 117(50), 13636–13647.
Résumé: The microwave spectra of the 3,4- (syn and anti), 2,5- (syn), and 3,5-dimethylbenzaldehyde (DMBA) molecules have been recorded for the first time in the 2–26.5 GHz frequency range, using the high resolution COBRA-FTMW spectrometer in Hannover. The experimental assignments and fits are supplemented by ab initio quantum chemical calculations of the conformational energy landscape and dipole moment components. The analysis of the spectra of the four observed isomers, including spectroscopic constants and large amplitude motion parameters, are presented in this paper. The DMBA isomers belong to a series of similar molecules obtained formally by adding one or more methyl group(s) at the aromatic ring. These molecules serve as prototype systems for the development of the theoretical model of asymmetric top molecules having Cs symmetry while containing in addition two nonequivalent methyl tops (C3v), exhibiting different barrier heights and coupling terms. Thus, the DMBA isomers represent good species for testing the recently written two-top internal rotors BELGI program.
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Vander Auwera, J., Ngo, N. H., El Hamzaoui, H., Capoen, B., Bouazaoui, M., Ausset, P., & Boulet, C. and H., J.-M. (2013). Infrared absorption by molecular gases as a probe of nanoporous silica xerogel and molecule-surface collisions: Low-pressure results. PHYSICAL REVIEW A, 88(042506), 042506.
Résumé: Transmission spectra of gases confined (but not adsorbed) within the pores of a 1.4-cm-thick silica xerogel sample have been recorded between 2.5 and 5 μm using a high-resolution Fourier transform spectrometer. This was done for pure CO, CO2, N2O, H2O, and CH4 at room temperature and pressures of a few hectopascals. Least-squares fits of measured absorption lines provide the optical-path lengths within the confined (LC) and free (LF) gas inside the absorption cell and the half width at half maximum ΓC of the lines of the confined gases. The values of LC and LF retrieved using numerous transitions of all studied species are very consistent. Furthermore, LC is in satisfactory agreement with values obtained from independent measurements, thus showing that reliable information on the open porosity volume can be retrieved from an optical experiment. The values of ΓC, here resulting from collisions of the molecules with the inner surfaces of the xerogel pores, are practically independent of the line for each gas and inversely proportional to the square root of the probed-molecule molar mass. This is a strong indication that, for the studied transitions, a single collision of a molecule with a pore surface is sufficient to change its rotational state. A previously proposed simple model, used for the prediction of the line shape, leads to satisfactory agreement with the observations. It also enables a determination of the average pore size, bringing information complementary to that obtained from nitrogen adsorption porosimetry.
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Veyrinas, K., Elkharrat, C., Marggi Poullain, S., Saquet, N., Dowek, D., Lucchese, R. R., Garcia, G. A., & Nahon, L. (2013). Complete determination of the state of elliptically polarized light by electron-ion vector correlations. PHYSICAL REVIEW A, 88(6), 063411.
Résumé: We propose a method, molecular polarimetry, applicable to an extended VUV-x-ray range, allowing us to determine the complete state of elliptically polarized light, including the challenging disentanglement of the circular and unpolarized components. It relies on the determination of the molecular frame photoelectron angular distributions derived from electron-ion velocity vector correlations in dissociative photoionization of simple molecules. The high accuracy of the full set of Stokes parameters determination has been established by comparison with data obtained in parallel with a VUV optical polarimeter used as a benchmark.
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Videcoq, P., Steenkeste, K., Bonnin, E., & Garnier C. (2013). A multi-scale study of enzyme di ff usion in macromolecular solutions and physical gels of pectin polysaccharides. Soft Matter, 9, 5110–5118.
Résumé: Pectin accounts for one of the major polysaccharides of the plant cell wall. Pectin methylesterases (PMEs)are enzymes that are able to alter the pectin structure and affect its gelling properties by de-esterifying galacturonic acid. In this work, the diffusion of two PMEs with different origins and modes of action
was characterised with a multi-scale approach in different media consisting of pectin macromolecular solutions and physical gels. Fluorescence Recovery After Photobleaching (FRAP) and Fluorescent Correlation Spectroscopy (FCS) investigations showed similar diffusion behaviour for both enzymes at a microscopic scale. In contrast, their behaviours tended to differ when increasing the observation scale up to mm. Indeed, fungal PMEs diffused faster and in a larger range than plant PMEs. These results are discussed with regard to the respective modes of action, processivity and in vivo roles of the two enzymes.
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Vieillard, T., Chaussard, F., Billard, F., Sugny, D., Faucher, O., Ivanov, S., Hartmann, J. - M., Boulet, C., & Lavorel, B. (2013). Field-free molecular alignment for probing collisional relaxation dynamics. PHYSICAL REVIEW A, 87(2), 023409.
Résumé: We report the experimental study of field-free molecular alignment in CO2 gas mixtures induced by intense femtosecond laser pulses in the presence of collisional processes. We demonstrate that the alignment signals exhibit specific features due to nontrivial collisional propensity rules that tend to preserve the orientation of the rotational angular momentum of the molecules. The analysis is performed with a quantum approach based on the modeling of rotational J- and M-dependent state-to-state transfer rates. The present work paves the way for strong-field spectroscopy of collisional dynamics. DOI: 10.1103/PhysRevA.87.023409
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Vizzini, S., Oughaddou, H., Hoarau, J. Y., Biberian, J. P., Bertoglio, M., & Aufray, B. (2013). Unexpected behaviour of one Pb monolayer deposited on aluminum oxide thin film grown on Ag(111). APPLIED PHYSICS LETTERS, 103(26), 261601.
Résumé: Using scanning tunneling microscopy (STM), Auger electron spectroscopy, and low energy electron diffraction, we have observed a surprising complete dissolution at room temperature of one lead monolayer deposited by evaporation on an aluminum oxide thin film (similar to 0.8 nm thick) previously grown on Ag (111). We have observed the quasi-instantaneous diffusion of the lead deposit through the oxide layer to the silver/oxide interface. After the diffusion process, lead atoms form a Moire superstructure, which is characterized by STM through the oxide layer. This unexpected behavior puts in light the very weak interaction between the aluminum oxide and the silver substrate. (C) 2013 AIP Publishing LLC.
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Wang, C. Y., Herr, T., Del'Haye, P., Schliesser, A., Hofer, J., Holzwarth, R., Haensch, T. W., Picque, N., & Kippenberg, T. J. (2013). Mid-infrared optical frequency combs at 2.5 μm based on crystalline microresonators. NATURE COMMUNICATIONS, 4, 1345.
Résumé: The mid-infrared spectral range (lambda similar to 2-20 μm) is of particular importance as many molecules exhibit strong vibrational fingerprints in this region. Optical frequency combs-broadband optical sources consisting of equally spaced and mutually coherent sharp lines-are creating new opportunities for advanced spectroscopy. Here we demonstrate a novel approach to create mid-infrared optical frequency combs via four-wave mixing in a continuous-wave pumped ultra-high Q crystalline microresonator made of magnesium fluoride. Careful choice of the resonator material and design made it possible to generate a broadband, low-phase noise Kerr comb at lambda = 2.5 μm spanning 200 nm (approximate to 10 THz) with a line spacing of 100 GHz. With its distinguishing features of compactness, efficient conversion, large mode spacing and high power per comb line, this novel frequency comb source holds promise for new approaches to molecular spectroscopy and is suitable to be extended further into the mid-infrared.
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Yang, H., Mayne, A. J., Cejas, C., Dujardin, G., & Kuk, Y. (2013). Manipulation at a distance: Atomic-scale observation of ballistic electron transport in single layer graphene. Appl. Phys. Lett., 102(22), 223104.
Résumé: We present scanning tunneling microscopy manipulation experiments on epitaxial graphene and the carbon buffer layer grown on hexagonal silicon carbide. Low voltage pulses applied to the graphene layer with the microscope tip induce nonlocal modifications of a bare carbon buffer region 10 nm away. The graphene itself is not affected. This is direct evidence for ballistic hot electrons propagating along the graphene layer to the graphene edge. High energy states in the graphene band structure (Van Hove Singularities) may explain both the electron transport and the coupling of the graphene edge to the adjacent bare carbon buffer region.
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Yang, H., Mayne, A. J., Comtet, G., Dujardin, G., Kuk, Y., Sonnet, P., Stauffer, L., Nagarajan, S., & Gourdon, A. (2013). STM imaging, spectroscopy and manipulation of a self-assembled PTCDI monolayer on epitaxial graphene. Phys. Chem. Chem. Phys., 15(14), 4939–4946.
Résumé: Scanning Tunneling Microscopy (STM), Scanning Tunneling Spectroscopy (STS), and manipulation studies were performed on an ordered self-assembled monolayer (SAM) of N,N'-bis(1-hexylheptyl)perylene-3,4: 9,10-bis(dicarboximide) molecules on epitaxial graphene on hexagonal silicon carbide – SiC(0001). Four novel aspects of the molecular SAM on graphene are presented. Molecules adsorb in both armchair and zig-zag configurations, giving rise to six orientations of the molecular layer with respect to the underlying substrate. The interaction between the molecules and the graphene surface shifts the LUMO towards the Fermi level, inducing a charge transfer and the opening of a band gap in the graphene, with the LUMO inside. This decouples the LUMO from the surface rendering it invisible in the dI/dV spectroscopy. The HOMO only becomes visible at short tip-surface distances, as its energy lies within the band gap of the SiC substrate. Finally, the observed molecular defects are very particular, being composed exclusively of molecular dimers. These molecular dimers have a stronger interaction with the graphene than other molecules.
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Zhang, Y., Boer-Duchemin, E., Wang, T., Rogez, B., Comtet, G., Le Moal, E., Dujardin, G., Hohenau, A., Gruber, C., & Krenn, J. R. (2013). Edge scattering of surface plasmons excited by scanning tunneling microscopy. Opt. Express, 21(12), 13938–13948.
Résumé: The scattering of electrically excited surface plasmon polaritons (SPPs) into photons at the edges of gold metal stripes is investigated. The SPPs are locally generated by the inelastic tunneling current of a scanning tunneling microscope (STM). The majority of the collected light arising from the scattering of SPPs at the stripe edges is emitted in the forward direction and is collected at large angle (close to the air-glass critical angle, θc). A much weaker isotropic component of the scattered light gives rise to an interference pattern in the Fourier plane images, demonstrating that plasmons may be scattered coherently. From these results, we interpret the directional, large angle scattering to be mainly from plasmons on the air-gold interface, and the diffuse scattering forming interference fringes to be dominantly from plasmons on the gold-substrate interface.
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Zugarramurdi, A., & Borisov, A. G. (2013). Theoretical study of the effect of beam misalignment in fast-atom diffraction at surfaces. Phys. Rev. A, 87(6), 062902.
Résumé: Typical applications of the fast-atom diffraction technique exploit incidence along low-index directions to extract accurate structural information on surfaces from the diffraction pattern. The data interpretation in this case is well developed and simplified by the axial channeling conditions, where the three-dimensional projectile-surface interaction appears effectively averaged over the fast-motion direction. We study theoretically the diffraction of fast-atom beams that are significantly misaligned with respect to a low-index direction at the surface. With full quantum wave-packet calculations, we address He atom scattering from the LiF(001) surface within a wide range of azimuthal and polar incidence angles. In particular, we are interested in the transitions between low-index directions upon the azimuthal rotation of the beam, and in the question of the choice of an adequate axial channeling approximation. We make use of the energy criterion to analyze the diffraction patterns and to discuss how the momentum exchange projected on the beam direction affects the diffraction.
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Zugarramurdi, A., & Borisov, A. G. (2013). When fast atom diffraction turns 3D. Nucl. Instrum. Methods Phys. Res., B, 317, 83–89.
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Zugarramurdi, A., Debiossac, M., Lunca-Popa, P., Alarcon, L. S., Momeni, A., Khemliche, H., Roncin, P., & Borisov, A. G. (2013). Surface-grating deflection of fast atom beams. Phys. Rev. A, 88(1), 0129074.
Résumé: For energetic atomic beams grazingly incident at the surface along the low index directions, fast motion parallel to the surface and slow motion perpendicular to the surface lead to the quantum diffraction pattern in the scattered beam. In this experimental and theoretical joint study we show that when the incident beam is misaligned with respect to an axial channel, the characteristic deformation of the diffraction pattern reflects an overall deflection of the scattered beam from the specular direction. The deflection is maximum for the azimuthal misalignment angles close to the rainbow angle and we show how this effect can be explained with the detailed balance principle relating diffraction of misaligned and perfectly aligned beams. We also demonstrate that using the detailed balance principle the diffraction charts for the incident beams aligned along the axial channel can be reconstructed from the azimuthal incidence angle dependence of the data obtained with misaligned beams.
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Procédures de Conférences |
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Klisnick, A., & Menoni, C. S. (2013). X-Ray Lasers and Coherent X-Ray Sources: Development and Applications X Introduction (Vol. 8849).
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Actes de Conférences |
Barroca, T., Bon, P., Leveque-Fort, S., & Fort, E. (2013). Supercritical self-interference fluorescence microscopy for full-field membrane imaging. In Three-Dimensional And Multidimensional Microscopy: Image Acquisition And Processing Xx (Vol. 8589).
Résumé: We present a new technique based on the self-interference of Supercritical Angle Fluorescence (SAF) emission in order to perform full-field cell membrane imaging. We show that our Point Spread Function (PSF) engineering technique allows us to obtain a 100 nm axial sectioning while conserving the original lateral resolution of the microscope. The images are acquired using an optical module that can be connected to any fluorescent microscope to simultaneously monitor in real time both the cell membrane and in-depth phenomena.
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Bon, P., Barroca, T., Leveque-Fort, S., & Fort, E. (2013). Supercritical scattering microscopy for quantitative phase in the vicinity of a lamella. In Three-Dimensional And Multidimensional Microscopy: Image Acquisition And Processing Xx (Vol. 8589).
Résumé: In this paper, we discuss the possibility of making a super-axially-resolved image of a biological sample using supercritical angle diffusion. This labeling-free approach is suitable to any microscope equipped with a N A(obj) > 1.33 microscope objective and can be used either for conventional intensity imaging or for quantitative phase imaging. We expose some results on beads an cells showing the potential of this method.
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Carpentier, Y., Feraud, G., Dartois, E., Brunetto, R., Charon, E., Cao, A. T., d'Hendecourt, L., Brechignac, P., Rouzaud, J. N., & Pino, T. (2013). NANOSTRUCTURATION OF POLYAROMATIC ANALOGUES OF THE CARBONACEOUS DUST. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 399–404).
Résumé: Carbonaceous cosmic dust is mainly observed through infrared spectroscopy either in absorption or in emission. Laboratory soot analogues of this interstellar or circumstellar dust were produced in fuel-rich, low-pressure, premixed and flat, flames. The particles were investigated by infrared absorption spectroscopy in the 2-15 μm spectral region. The details of the spectral features shed some light on the structure of the material and enable the study of its life cycle. In particular, the 8 μm band position is tentatively attributed to defects at the edge or in the polyaromatic units of the materials, revealing these structural changes in astrophysical dust.
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Dupuis, G., Benabdallah, N., Chopinaud, A., Mayet, C., & Leveque-Fort, S. (2013). Time-resolved wide-field optically sectioned fluorescence microscopy. In Three-Dimensional And Multidimensional Microscopy: Image Acquisition And Processing Xx (Vol. 8589).
Résumé: We present the implementation of a fast wide-field optical sectioning technique called HiLo microscopy on a fluorescence lifetime imaging microscope. HiLo microscopy is based on the fusion of two images, one with structured illumination and another with uniform illumination. Optically sectioned images are then digitally generated thanks to a fusion algorithm. HiLo images are comparable in quality with confocal images but they can be acquired faster over larger fields of view. We obtain 4-D imaging by combining HiLo optical sectioning, time-gated detection, and z-displacement. We characterize the performances of this set-up in terms of 3-D spatial resolution and time-resolved capabilities in both fixed- and live-cell imaging modes.
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Feraud, G., Carpentier, Y., Pino, T., Longval, Y., Dartois, E., Chamaille, T., Vasquez, R., Vincent, J., Parneix, P., Falvo, C., & Brechignac, P. (2013). INFRARED EMISSION FROM PHOTO-EXCITED GASEOUS BENZENE: DETECTION WITH A NEW HOME-MADE SPECTROMETER. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 379–384).
Résumé: The infrared fluorescence decay and the dispersed emission spectrum are presented for gaseous benzene following 193 nm laser excitation. They were measured with FIREFLY (Fluorescence in the Infra Red from Excited FLYing molecules), a new home-made spectrometer. Redshift and redtail in the CH stretch emission spectra (3.3 μm region) demonstrate that anharmonicity plays a key role when dealing with high internal energies, as it is the case in the interstellar medium.
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Friha, H., Feraud, G., Pino, T., Parneix, P., Dhaouadi, Z., & Brechignac, P. (2013). ELECTRONIC SPECTRA OF CATIONIC PAH AND PAH CLUSTERS. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 373–378).
Résumé: An experiment designed for measuring the electronic spectra of PAH cations and PAH cluster cations has been set up, which is briefly described. The photodissociation spectra, reflecting the absorption spectra, of 2-methyl-naphthalene dimer cation have been recorded in the spectral ranges corresponding to the transitions from the ground state to both the excited charge resonance state and the first allowed local electronic excitation state.
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Godard, M., Feraud, G., Chabot, M., Carpentier, Y., Pino, T., Brunetto, R., Duprat, J., Engrand, C., Brechignac, P., d'Hendecourt, L., & Dartois, E. (2013). EFFECTS OF COSMIC RAYS ON HYDROCARBON INTERSTELLAR DUST. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 395–398).
Résumé: Hydrogenated amorphous carbons, an important component of the interstellar carbonaceous dust, possess infrared spectral signatures (at 3.4, 6.9 and 7.3 μm) that are ubiquitous in the diffuse interstellar medium of galaxies, but not observed in dense clouds. To better understand the role played by cosmic rays in the disappearance of these absorption bands, irradiation experiments of hydrocarbon dust analogues have been performed with different swift ions. The results obtained through the in situ infrared monitoring of the samples during the irradiations allow to infer the dehydrogenation effect of the cosmic ray distribution on the interstellar hydrogenated amorphous carbons. The importance of this interstellar dust destruction by cosmic rays is discussed in comparison to other energetic processes in different interstellar environments.
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Holzner, S., Ideguchi, T., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Dual-Comb Coherent Raman Spectro-Imaging. In 2013 Conference On Lasers And Electro-Optics Pacific Rim (Cleo-Pr).
Résumé: Ultra-rapid coherent Stokes and anti-Stokes Raman spectroscopy with two laser frequency combs is demonstrated. Spectra and hyperspectral images are measured over a span of 1200 cm(-1) at 4 cm(-1) resolution within 15 microseconds.
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Holzner, S., Ideguchi, T., Guelachvili, G., Hansch, T. W., & Picque, N. (2013). Simultaneous Coherent Stokes and Anti-Stokes Raman Spectroscopy with Two Laser Frequency Combs. In 2013 Conference On Lasers And Electro-Optics (Cleo).
Résumé: We present a new technique of non-linear dual-comb spectroscopy for the measurement of coherent Stokes and anti-Stokes Raman spectra of fundamental vibrational transitions. Ultra-rapid acquisition times, high-resolution, broad-spectral-span are the main characteristics of our experiments.
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Coherent anti-Stokes Raman dual-comb spectro-microscopy. In 2013 Conference On Lasers And Electro-Optics (Cleo).
Résumé: Ultra-rapid coherent anti-Stokes Raman spectroscopy with two laser frequency combs is demonstrated. Hyperspectral images are acquired over a spectral bandwidth of 1200 cm(-1) with a resolution of 10 cm(-1) at a rate of 50 pixels/s.
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Ultra-rapid coherent anti-Stokes Raman dual-comb spectroscopy and microscopy. In 2013 Conference On And International Quantum Electronics Conference Lasers And Electro-Optics Europe (Cleo Europe/Iqec).
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Ideguchi, T., Poisson, A., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Adaptive Dual-Comb Spectroscopy with Free-Running Lasers. In 2013 Conference On Lasers And Electro-Optics Pacific Rim (Cleo-Pr).
Résumé: A new concept of real-time dual-comb spectroscopy that only uses free-running femtosecond mode-locked lasers provides high quality Fourier spectra with resolved comb lines over 12 THz spectral span without a posteriori data processing.
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Klisnick, A., Meng, L. M., Le Marec, A., & Larroche, O. (2013). Modeling and numerical simulations of seeded XUV lasers with the COLAX code: recent progress. In X-Ray Lasers And Coherent X-Ray Sources: Development And Applications X (Vol. 8849).
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