Peer-reviewed Publications |
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Aguirregabiria, G., Marinica, D. C., Esteban, R., Kazansky, A. K., Aizpurua, J., & Borisov, A. G. (2018). Role of electron tunneling in the nonlinear response of plasmonic nanogaps. Phys. Rev. B, 97(11), 115430.
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Alekseyev, A. B., Liebermann, H. - P., Vazquez, G. J., & Lefebvre-Brion, H. (2018). Coupled-channel study of the Rydberg-valence interaction in HBr. J Chem Phys, 148(8), 084302.
Résumé: We report an ab initio study of the low-lying valence and Rydberg states of HBr. The calculations are carried out employing the multireference single- and double-excitation configuration interaction method including the spin-orbit interaction. The first excited adiabatic potential of (1)Sigma(+) symmetry presents two minima which correspond to the Rydberg E(1)Sigma(+) and valence V(1)Sigma(+) observed states. We calculate the vibrational levels of these two states using a coupled-channel treatment based on the two diabatic potentials deduced from the ab initio adiabatic potentials and the Rydberg-valence interaction. The chaotic energy separations between the observed levels are well reproduced in the calculations. We have also obtained for the first time theoretical data for numerous Rydberg states of HBr lying in the (66-79) x 10(3) cm(-1) excitation energy interval. The calculated spectroscopic parameters are found to be in good agreement with experiment and provide a basis for future studies of radiative and non-radiative processes in the HBr molecule.
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Alyabyeva, N., Ouvrard, A., Lindfors-Vrejoiu, I., Kolomiytsev, A., Solodovnik, M., Ageev, O., & McGrouther, D. (2018). Modified cantilevers to probe unambiguously out-of-plane piezoresponse. Phys. Rev. Mater., 2(6), 064402.
Résumé: We demonstrate and investigate the coupling of contributions from both in-plane (IP) polarization and out-of-plane (OP) components in BiFeO3 (BFO) thin-film polarization probed by piezoresponse force microscopy (PFM). Such coupling leads to image artifacts which prevent the correct determination of OP polarization vector directions and the corresponding piezoelectric coefficient d33. Using material strength theory with a one-dimensional modeling of the cantilever oscillation amplitude under electrostatic and elastic forces as a function of the tip length, we have evidenced the impact of IP piezoresponse to the OP signal for tip length longer than 4 μm. The IP polarization vector induces a significant longitudinal bending of the cantilever, due to the small spring constant of long tips, which provokes a normal deviation superimposed to the OP piezoresponse. These artifacts can be reduced by increasing the longitudinal spring constant of the cantilever by shortening the tip length. Standard cantilevers with 15-μm-long tips were modified to reach the desired tip length, using focused ion-beam techniques and tested using PFM on the same BFO thin film. Tip length shortening has strongly reduced IP artifacts as expected, while the impact of nonlocal electrostatic forces, becoming predominant for tips shorter than 1 μm, has led to a non-negligible deflection offset. For shorter tips, a strong electric field from a cantilever beam can induce polarization switching as observed for a 0.5-μm-long tip. Tip length ranging from 1 to 4 μm allowed minimizing both artifacts to probe unambiguously OP piezoresponse and quantify the d33 piezoelectric coefficient.
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Alyabyeva, N., Ouvrard, A., Zakaria, A. - M., Charra, F., & Bourguignon, B. (2018). Transition from disordered to long-range ordered nanoparticles on Al 2 O 3 /Ni 3 Al(111). Appl. Surf. Sci., 444, 423–429.
Résumé: Application of preparation recipes of the literature failed to produce an ordered array of NPs on our particular Ni3Al sample. This has motivated a systematic survey of Pd NP nucleation as a function of experimental parameters. We have shown that the increase of oxidation temperature during the preparation of Al2O3 ultra-thin film on Ni3Al(111) leads to a transition from disordered to long-range ordered Pd nanoparticle (NP) nucleation. Alumina films were prepared at different temperatures ranging from 990 to 1140 K. Crystallinity, electronic structure of the alumina film and Pd nucleation and growth have been investigated using Low Energy Electron Diffraction and Scanning Tunnelling Microscopy. NP density and long-range order nucleation along the so-called “dot structure” of 4.2 nm periodicity, strongly increase for temperatures higher than a threshold value of 1070 ± 20 K. This transition relies on the alumina film improvement and suggests that the modulation of Pd adsorption energy at nucleation centres which is necessary to nucleate NPs at ordered sites, requires higher preparation temperature. Long-range ordered NPs with a high density were obtained 140 K above reported recipes in the literature. This optimized temperature has been tested on a fresh sample (issued from the same supplier) for which just a few cleanings were enough to obtain long-range ordered NPs. Presumably the variability of the optimal oxidation temperature for our samples with respect to the literature is related to fluctuations of the stoichiometry from sample to sample.
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Augé, B., Been, T., Boduch, P., Chabot, M., Dartois, E., Madi, T., Ramillon, J. M., Ropars, F., Rothard, H., & Voivenel, P. (2018). IGLIAS: A new experimental set-up for low temperature irradiation studies at large irradiation facilities. Review of Scientific Instruments, 89(7), 075105.
Résumé: We designed and built a mobile experimental set-up for studying the interaction of ion beams with solid samples in a wide temperature range from 9 to 300 K. It is either possible to mount up to three samples prepared ex situ or to prepare samples by condensation of molecules from gases or vapours onto IR or Visible-ultraviolet (Vis-UV) transparent windows. The physico-chemical evolution during irradiation can be followed in situ with different analysis techniques including Fourier transform infrared spectroscopy, Vis-UV, and quadrupole mass spectrometry.
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Babikov, D., Benoit, D., Bowman, J., Burd, T., Clary, D., Donovan, R., Fischer, I., Gianturco, F., Hochlaf, M., Kar, S., Kirrander, A., Leone, S., Malcomson, T., Manthe, U., McCoy, A. B., Petersen, J., Richardson, J., Slavicek, P., Stoecklin, T., Szalewicz, K., van der Avoird, A., Wester, R., Worth, G., & Zehnacker-Rentien, A. (2018). Quantum dynamics of isolated molecules: general discussion. Faraday Discussions, 212, 281–306.
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Bacic, Z., Benoit, D., Besemer, M., Bowman, J., Bradforth, S., Clary, D., Donovan, R., Fischer, I., Gianturco, F., Hochlaf, M., Houston, P., Knowles, P., Leone, S., Linguerri, R., Manthe, U., McCoy, A. B., Petersen, J., Richardson, J., Shan, X., Slavicek, P., Stoecklin, T., Szalewicz, K., van der Avoird, A., Wester, R., Worth, G., & Zehnacker-Rentien, A. (2018). Precise characterisation of isolated molecules: general discussion. Faraday Discussions, 212, 137–155.
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Bacic, Z., Benoit, D., Biczysko, M., Bowman, J., Bradforth, S., Burd, T., Chambaud, G., Clary, D., Crepin, C., Dracinsky, M., Felker, P., Fischer, I., Gianturco, F., Hochlaf, M., Kouril, K., Kratochvilova, I., Liu, C. M., McCoy, A., Miyazaki, J., Mouhib, H., Richardson, J., Slavicek, P., Stoecklin, T., Szalewicz, K., van der Avoird, A., & Zehnacker-Rentien, A. (2018). Molecules in confinement in clusters, quantum solvents and matrices: general discussion. Faraday Discussions, 212, 569–601.
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Ban, L., Bowman, J., Bradforth, S., Chambaud, G., Dracinsky, M., Fischer, I., Gora, R., Hochlaf, M., Janicki, M., Kirrander, A., McCoy, A. B., Petersen, J., Richardson, J., Slavicek, P., Szalewicz, K., & Zehnacker-Rentien, A. (2018). Molecules in confinement in liquid solvents: general discussion. Faraday Discussions, 212, 383–397.
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Baraban, J. H., Martin-Drumel, M. - A., Changala, B., Eibenberger, S., Nava, M., Patterson, D., Stanton, J. F., Ellison, G. B., & McCarthy, M. C. (2018). The Molecular Structure of gauche-1,3-Butadiene: Experimental Establishment of Non-planarity. ANGEWANDTE CHEMIE, 57(7), 1821–1825.
Résumé: The planarity of the second stable conformer of 1,3-butadiene, the archetypal diene for the Diels–Alder reaction in which a planar conjugated diene and a dienophile combine to form a ring, is not established. The most recent high level calculations predicted the species to adopt a twisted, gauche structure owing to steric interactions between the inner terminal hydrogens rather than a planar, cis structure favored by the conjugation of the double bonds. The structure cis-1,3-butadiene is unambiguously confirmed experimentally to indeed be gauche with a substantial dihedral angle of 34°, in excellent agreement with theory. Observation of two tunneling components indicates that the molecule undergoes facile interconversion between two equivalent enantiomeric forms. Comparison of experimentally determined structures for gauche- and trans-butadiene provides an opportunity to examine the effects of conjugation and steric interactions.
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Barreau, L., Veyrinas, K., Gruson, V., Weber, S. J., Auguste T, Hergott, J. - F., Lepetit F, Carre B, Houver J.-C., Dowek, D., & Salieres, P. (2018). Evidence of depolarization and ellipticity of high harmonics driven by ultrashort bichromatic circularly polarized fields. Nat Commun, 9, 4727.
Résumé: High harmonics generated by counter-rotating laser fields at the fundamental and second harmonic frequencies have raised important interest as a table-top source of circularly polarized ultrashort extreme-ultraviolet light. However, this emission has not yet been fully characterized: in particular it was assumed to be fully polarized, leading to an uncertainty on the effective harmonic ellipticity. Here we show, through simulations, that ultrashort driving fields and ultrafast medium ionization lead to a breaking of the dynamical symmetry of the interaction, and consequently to deviations from perfectly circular and fully polarized harmonics, already at the single-atom level. We perform the complete experimental characterization of the polarization state of high harmonics generated along that scheme, giving direct access to the ellipticity absolute value and sign, as well as the degree of polarization of individual harmonic orders. This study allows defining optimal generation conditions of fully circularly polarized harmonics for advanced studies of ultrafast dichroisms.
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Battandier, M., Bonal, L., Quirico, E., Beck, P., Engrand, C., Duprat, J., & Dartois, E. (2018). Characterization of the organic matter and hydration state of Antarctic micrometeorites: A reservoir distinct from carbonaceous chondrites. Icarus, 306, 74–93.
Résumé: This work presents a multi-analysis on 35 Antarctic micrometeorites (AMMs) (Concordia collection 2006) by coupled Raman and Infrared (IR) spectroscopies, in comparison with samples from type 1 and 2 carbonaceous CM, CR and CI chondrites. We identified the Raman G- and D-bands revealing the presence of polyaromatic carbonaceous material on raw particles in a subset of 16 particles. Thirteen AMMs (10 Fg + 1 Fg-Sc + 1 Sc) were selected from this first subset, and analyzed by infrared microscopy along with 4 AMMs (2 Fg + 1 Fg-Sc + 1 Sc) from a previous study by Dobrica et al. (2011). These analyses showed that scoriaceous, fine-grained scoriaceous and part of the fine-grained AMMs are not hydrated, with a weak abundance of carbonaceous matter. According to the Raman criterion defined by Dobrica et al. (2011), hydrous AMMs do not show structural modifications induced by heating through the atmospheric entry. In several hydrous AMMs, the carbonaceous matter abundance is found larger than in Orgueil (CI), Murchison (CM) and QUE 99177 (CR) chondrites and their mineral content exhibit differences reflected by the structure of the silicate 10 µm band. These observations suggest that part of the AMMs originates from one, or several, distinct parent bodies with respect to primitive carbonaceous chondrites. Each hydrous Fg-AMMS displays higher CH2/CH3 ratio and a smaller carbonyl abundance than chondrites, which point toward a mild processing during atmospheric entry, possibly oxidation, which did not modify the carbon backbone and therefore do not induce differences in Raman spectroscopy.
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Becker D., Lachmann M. D., Seidel S. T., Ahlers H., Amri S., Charron E., Corgier R., Franz T., Gaaloul N., Grosse J., Hellmig O., Herr W., Lüdtke D., Müntinga H., Popp M., Schkolnik V., Wendrich T., Wenzlawski A., Weps B., Braxmeier C., Ertmer W., Krutzik M., Lämmerzahl C., Peters A., Schleich W. P., Sengstock K., Walser R., Windpassinger P., & Rasel E. M. (2018). Space-borne Bose-Einstein condensation for precision interferometry. Nature, 562, 391.
Résumé: Owing to the low-gravity conditions in space, space-borne laboratories enable experiments with extended free-fall times. Because Bose–Einstein condensates have an extremely low expansion energy, space-borne atom interferometers based on Bose–Einstein condensation have the potential to have much greater sensitivity to inertial forces than do similar ground-based interferometers. On 23 January 2017, as part of the sounding-rocket mission MAIUS-1, we created Bose–Einstein condensates in space and conducted 110 experiments central to matter-wave interferometry, including laser cooling and trapping of atoms in the presence of the large accelerations experienced during launch. Here we report on experiments conducted during the six minutes of in-space flight in which we studied the phase transition from a thermal ensemble to a Bose–Einstein condensate and the collective dynamics of the resulting condensate. Our results provide insights into conducting cold-atom experiments in space, such as precision interferometry, and pave the way to miniaturizing cold-atom and photon-based quantum information concepts for satellite-based implementation. In addition, space-borne Bose–Einstein condensation opens up the possibility of quantum gas experiments in low-gravity conditions.
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BenNasr, F., Perez-Mellor, A., Alata, I., Lepere, V., Jaidane, N. E., & Zehnacker, A. (2018). Stereochemistry-dependent hydrogen bonds stabilise stacked conformations in jet-cooled cyclic dipeptides: (LD) vs. (LL) cyclo tyrosine-tyrosine. Faraday Discussions, 212, 399–419.
Résumé: Tyrosine-containing cyclic dipeptides based on a diketopiperazine (DKP) ring are studied under jet-cooled conditions using resonance-enhanced multi-photon ionisation (REMPI), conformer-selective IR-UV double resonance vibrational spectroscopy and quantum chemical calculations. The conformational landscape of the dipeptide containing natural L tyrosine (Tyr), namely c-LTyr-LTyr strongly differs from that of its diastereomer c-LTyr-DTyr. A similar family of conformers exists in both systems, with one aromatic ring folded on the dipeptide DKP ring and the other one extended. Weak NH and CH interactions are observed, which are slightly different in c-LTyr-LTyr and c-LTyr-DTyr. These structures are identical to those of LL and LD cyclo diphenylalanine, which only differ from c-Tyr-Tyr by the absence of hydroxyl on the benzene rings. While this is the only conformation observed for c-LTyr-DTyr, c-LTyr-LTyr exhibits an additional form stabilised by the interaction of the two hydroxyls, in which the two aromatic rings are in a stacked geometry. Stereochemical effects are still visible in the radical cation, for which one structure is observed for c-LTyr-DTyr, while the spectrum of the c-LTyr-LTyr radical cation is explained in terms of two co-existing structures.
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Blancard C., Cubaynes D., Guilbaud S., & and Bizau J.-M. (2018). Absolute Photoionization Cross Section for Fe6+ to Fe10+ Ions in the Photon Energy Region of the 2p–3d Resonance Lines. The Astrophysical Journal, 853(1), 32.
Résumé: Resonant single photoionization cross sections of Fen+ (n = 6 to 10) ions have been measured in absolute values using a merged-beams setup at the SOLEIL synchrotron radiation facility. Photon energies were between about 710 and 780 eV, covering the range of the 2p–3d transitions. The experimental cross sections are compared to calculations we performed using a multi-configuration Dirac–Fock code and the OPAS code dedicated to radiative opacity calculations. Comparisons are also done with the Chandra X-ray observatory NGC 3783 spectra and with the results of previously published calculations.
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Bocquet, F. C., Giovanelli, L., Ksari, Y., Ovramenko, T., Mayne, A. J., Dujardin, G., Spillebout, F., Sonnet, P., Bondino, F., Magnano, E., & Themlin, J. - M. (2018). Peculiar covalent bonding of C60/6H-SiC(0001)-(3 × 3) probed by photoelectron spectroscopy. J. Phys. Condens. Matter., 30(50), 505002.
Résumé: High resolution photoemission with synchrotron radiation was used to study the interface formation of a thin layer of C60 on 6H-SiC(0 0 0 1)-(3 × 3), characterized by protruding Si-tetramers. The results show that C60 is chemisorbed by orbital hybridization between the highest-occupied molecular orbital (HOMO) and the p z orbital of Si adatom at the apex of the tetramers. The covalent nature of the bonding was inferred from core level as well as valence band spectra. The Si 2p spectra reveal that a large fraction (at least 45%) of the Si adatoms remain unbound despite the reactive character of the associated dangling bonds. This is consistent with a model in which each C60 is attached to the substrate through a single covalent C60–Si bond. A binding energy shift of the core levels associated with sub-surface Si or C atoms indicates a decrease of the SiC band bending caused by a charge transfer from the C60 molecules to the substrate via the formation of donor-like interface states.
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Bouchet, A., Klyne, J., Ishiuchi, S. - I., Dopfer, O., Fujii, M., & Zehnacker, A. (2018). Stereochemistry-dependent structure of hydrogen-bonded protonated dimers: the case of 1-amino-2-indanol. Phys Chem Chem Phys, 20, 12430–12443.
Résumé: To understand the role of chirality in shaping biological supramolecular systems it is instructive to visualize the subtle effects of stereochemistry on the structure of model aggregates at the molecular level. Here, we apply conformer-specific IR-UV double-resonance laser spectroscopy in a cold ion trap to derive a detailed description of the protonated homodimers of (1R,2S)-cis- and (1R,2R)-trans-1-amino-2-indanol (c-AI2H+, t-AI2H+). Although the protonated monomers (c-AIH+, t-AIH+) only differ by the chirality of one carbon atom, their conformations are clearly distinct. c-AIH+ has an intramolecular NH+O hydrogen bond (H-bond), while t-AIH+ lacks such an interaction. This has crucial consequences on the geometry and stability of the corresponding c-AI2H+ and t-AI2H+ dimers. While there is a competition between intra- and intermolecular H-bonds in c-AI2H+, the formation of t-AI2H+ does not require deformation of the monomers. This difference results in higher binding energies of t-AI2H+ compared to c-AI2H+. To optimize the H-bond network, the two dimers do not necessarily involve the corresponding most stable monomers. c-AI2H+ and t-AI2H+ differ in their UV photodissociation mass spectra and in their electronic spectra, which suggests different geometries also in the excited state.
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Boudjemaa, R., Cabriel, C., Dubois-Brissonnet, F., Bourg, N., Dupuis, G., Gruss, A., Lévêque-Fort, S., Briandet, R., Fontaine-Aupart, M.-P., Steenkeste K. (2018). Failure of daptomycin to kill Staphylococcus aureus: impact of bacterial membrane fatty acid composition. Antimicrobial Agents and Chemotherapy, .
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Boudjemaa, R., Steenkeste, K., Jacqueline, C., Briandet, R., Caillon, J., Boutoille, D., Le Mabecque, V., Tattevin, P., Fontaine-Aupart, M.P., Revest, M. (2018). Live intramacrophagic Staphylococcus aureus as possible responsible for antibiotic therapy failure: observations in an in-vivo mouse model of prosthetic vascular material infections. Journal of Antimicrobial Chemotherapy, .
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Bourguignon B. (2018). Pulse Shaping in Surface Science. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, , 604–610.
Résumé: Pulse shaping consists in adjusting the spectral and temporal shapes of a laser pulse to enhance the efficiency of specific laser-induced processes. Only ultrafast lasers have a suitable (broad enough) spectrum. Spatial pulse shaping is another type of shaping which consists in controlling the wave front profile to keep the beam spatially uniform and allow precise control of the energy distribution around the focus point. Pulse shaping has been developed to optimize the intrinsic quality of lasers, in particular to make ultrahigh intensity lasers, and to optimize specific light–matter interactions. In surface science, pulse shaping is mainly used for optimization of laser ablation and for Broad Band Sum Frequency Generation vibrational spectroscopy.
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Bryche, J. - F., Barbillon, G., Bartenlian, B., Dujardin, G., Boer-Duchemin, E., & Le Moal, E. (2018). k-space optical microscopy of nanoparticle arrays: Opportunities and artifacts. J. Appl. Phys., 124(4), 043102.
Résumé: We report on the performance and inherent artifacts of k-space optical microscopy for the study of periodic arrays of nanoparticles under the various illumination configurations available on an inverted optical microscope. We focus on the origin of these artifacts and the ways to overcome or even benefit from them. In particular, a recently reported artifact, called the “condenser effect,” is demonstrated here in a new way. The consequences of this artifact (which is due to spurious reflections in the objective) on Fourier-space imaging and spectroscopic measurements are analyzed in detail. The advantages of using k-space optical microscopy to determine the optical band structure of plasmonic arrays and to perform surface plasmon resonance experiments are demonstrated. Potential applications of k-space imaging for the accurate lateral and axial positioning of the sample in optical microscopy are investigated.
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Cabriel, C., Bourg, N., Dupuis, G., & Leveque-Fort, S. (2018). Aberration-accounting calibration for 3D single-molecule localization microscopy. Opt Lett, 43(2), 174–177.
Résumé: We propose a straightforward sample-based technique to calibrate the axial detection in 3D single-molecule localization microscopy. Using microspheres coated with fluorescent molecules, the calibration curves of point spread function-shaping or intensity-based measurements can be obtained over the imaging depth range. This experimental method takes into account the effect of the spherical aberration without requiring computational correction. We demonstrate its efficiency for astigmatic imaging in a 1.2 mum range above the coverslip.
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Cao, S., Le Moal, E., Jiang, Q., Drezet, A., Huant, S., Hugonin, J. - P., Dujardin, G., & Boer-Duchemin, E. (2018). Directional light beams by design from electrically driven elliptical slit antennas. Beilstein Journal of Nanotechnology, 9, 2361–2371.
Résumé: We report on the low-energy, electrical generation of light beams in specific directions from planar elliptical microstructures. The emission direction of the beam is determined by the microstructure eccentricity. A very simple, broadband, optical antenna design is used, which consists of a single elliptical slit etched into a gold film. The light beam source is driven by an electrical nanosource of surface plasmon polaritons (SPP) that is located at one focus of the ellipse. In this study, SPPs are generated through inelastic electron tunneling between a gold surface and the tip of a scanning tunneling microscope.
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Chin, A., Mangaud, E., Atabek, O., & Desouter-Lecomte, M. (2018). Coherent quantum dynamics launched by incoherent relaxation in a quantum circuit simulator of a light-harvesting complex. Phys. Rev. A, 97(6), 063823.
Résumé: Engineering and harnessing coherent excitonic transport in organic nanostructures has recently been suggested as a promising way towards improving manmade light-harvesting materials. However, realizing and testing the dissipative system-environment models underlying these proposals is presently very challenging in supramolecular materials. A promising alternative is to use simpler and highly tunable “quantum simulators” built from programmable qubits, as recently achieved in a superconducting circuit by Potočnik et al. [A. Potočnik et al., Nat. Commun. 9, 904 (2018)]. We simulate the real-time dynamics of an exciton coupled to a quantum bath as it moves through a network based on the quantum circuit of Potočnik et al. Using the numerically exact hierarchical equations of motion to capture the open quantum system dynamics, we find that an ultrafast but completely incoherent relaxation from a high-lying “bright” exciton into a doublet of closely spaced “dark” excitons can spontaneously generate electronic coherences and oscillatory real-space motion across the network (quantum beats). Importantly, we show that this behavior also survives when the environmental noise is classically stochastic (effectively high temperature), as in present experiments. These predictions highlight the possibilities of designing matched electronic and spectral noise structures for robust coherence generation that do not require coherent excitation or cold environments.
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Corgier R., Amri S., Herr W., Ahlers H., Guéry-Odelin D., Rasel E. M., Charron E., & Gaaloul N. (2018). Fast manipulation of Bose-Einstein condensates with an atom chip. New J. Phys., 20(5), 055002.
Résumé: We present a detailed theoretical analysis of the implementation of shortcut-to-adiabaticity protocols for the fast transport of neutral atoms with atom chips. The objective is to engineer transport ramps with durations not exceeding a few hundred milliseconds to provide metrologically relevant input states for an atomic sensor. Aided by numerical simulations of the classical and quantum dynamics, we study the behavior of a Bose-Einstein condensate in an atom chip setup with realistic anharmonic trapping. We detail the implementation of fast and controlled transports over large distances of several millimeters, i.e. distances 1000 times larger than the size of the atomic cloud. A subsequent optimized release and collimation step demonstrates the capability of our transport method to generate ensembles of quantum gases with expansion speeds in the picokelvin regime. The performance of this procedure is analyzed in terms of collective excitations reflected in residual center of mass and size oscillations of the condensate. We further evaluate the robustness of the protocol against experimental imperfections.
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Coudert, L. H. (2018). Optimal control of the orientation and alignment of an asymmetric-top molecule with terahertz and laser pulses. Journal of Chemical Physics, 148(9), 094306.
Résumé: Quantum optimal control theory is applied to determine numerically the terahertz and nonresonant laser pulses leading, respectively, to the highest degree of orientation and alignment of the asymmetric-top H2S molecule. The optimized terahertz pulses retrieved for temperatures of zero and 50 K lead after 50 ps to an orientation with ⟨ΦZx⟩ = 0.959 73 and ⟨⟨ΦZx⟩⟩ = 0.742 30, respectively. For the zero temperature, the orientation is close to its maximum theoretical value; for the higher temperature, it is below the maximum theoretical value. The mechanism by which the terahertz pulse populates high lying rotational levels is elucidated. The 5 ps long optimized laser pulse calculated for a zero temperature leads to an alignment with ⟨Φ2Zy⟩=0.94416
⟨ΦZy2⟩=0.944 16 and consists of several kick pulses with a duration of ≈0.1 ps. It is found that the timing of these kick pulses is such that it leads to an increase of the rotational energy of the molecule. The optimized laser pulse retrieved for a temperature of 20 K is 6 ps long and yields a lower alignment with ⟨⟨Φ2Zy⟩⟩=0.71720
⟨⟨ΦZy2⟩⟩=0.717 20.
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Coudert, L. H., Gans, B., Garcia, G. A., & Loison, J. - C. (2018). Renner-Teller effects in the photoelectron spectra of CNC, CCN, and HCCN. Journal of Chemical Physics, 148(5), 054302.
Résumé: The line intensity of photoelectron spectra when either the neutral or cationic species display a Renner-Teller coupling is derived and applied to the modeling of the photoelectron spectra of CNC, CCN, and HCCN. The rovibronic energy levels of these three radicals and of their cations are investigated starting from ab initio results. A model treating simultaneously the bending mode and the overall rotation is developed to deal with the quasilinearity problem in CNC+, CCN+, and HCCN and accounts for the large amplitude nature of their bending mode. This model is extended to treat the Renner-Teller coupling in CNC, CCN, and HCCN+. Based on the derived photoelectron line intensity, the photoelectron spectra of all three molecules are calculated and compared to the experimental ones.
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Coudert, L. H., Gans, B., Holzmeier, F., Loison, J. - C., Garcia, G. A., Alcaraz, C., Lopes, A., & Röder, A. (2018). Experimental and theoretical threshold photoelectron spectra of methylene. The Journal of Chemical Physics, 149(22), 224304.
Résumé: The threshold photoelectron spectrum of methylene (CH2), produced by consecutive H atom abstractions on methane, has been recorded using synchrotron radiation. The experimental spectrum spans the region of the X+ 2Πu ← X 3B1 ionizing transition. It is modeled starting from ab initio bending potentials and using the bending approach introduced by Coudert et al. [J. Chem. Phys. 148, 054302 (2018)] accounting for the quasilinearity of CH2 and the strong Renner-Teller interaction in CH2+. This first calculation yields a theoretical threshold photoelectron spectrum which is in moderate agreement with the experimental one. A more accurate approach treating the three vibrational modes is developed for computing the threshold photoelectron spectrum of triatomic C2v molecules. This new treatment is tested modeling the already measured threshold photoelectron spectrum of the X+ 2Πu ← X 1A1 ionizing transition of the water molecule. The threshold photoelectron spectrum of CH2 computed with the new approach compares more favorably with the experimental spectrum and yields an adiabatic ionization potential of 10.386(6) eV.
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Dartois, E., Chabot, M., Id Barkach, T., Rothard, H., Augé, B., Agnihotri, A. N., Domaracka, A., & Boduch, P. (2018). Cosmic ray sputtering yield of interstellar H2O ice mantles. A&A, 618, A173.
Résumé: Aims. Interstellar grain mantles present in dense interstellar clouds are in constant exchange with the gas phase via accretion and desorption mechanisms such as UV, X-ray photodesorption, cosmic ray induced sputtering, grain thermal fluctuations, and chemical reaction energy release. The relative importance of the various desorption mechanisms is of uttermost importance for astrophysical models to constrain the chemical evolution in such high density dense cloud regions.
Methods. The sputtering yields for swift ions simulating the effects of cosmic rays are most often measured in the semi-infinite limit using thick ice targets with the determination of the effective yield per incident ion. In this experimental work we investigated the sputtering yield as a function of ice mantle thickness, exposed to Xe ions at 95 MeV. The ion induced ice phase transformation and the sputtering yield were simultaneously monitored by infrared spectroscopy and mass spectrometry.
Results. The sputtering yield is constant above a characteristic ice layer thickness and then starts to decrease below this thickness. An estimate of the typical sputtering depth corresponding to this length can be evaluated by comparing the infinite thickness yield to the column density where the onset of the sputtering yield decrease occurs. In these experiments the measured characteristic desorption depth corresponds to ≈30 ice layers. Assuming an effective cylindrical shape for the volume of sputtered molecules, the aspect ratio is close to unity; in the semi-infinite ice film case this ratio is the diameter to height of the cylinder. This result shows that most ejected molecules arise from a rather compact volume. The measured infinite thickness sputtering yield for water ice mantles scales as the square of the ion electronic stopping power (Se, deposited energy per unit path length). Considering the experiments on insulators, we expect that the desorption depth dependence varies with Seα, where α ~ 1. Astrophysical models should take into account the thickness dependence constraints of these ice mantles in the interface regions when ices are close to their extinction threshold. In the very dense cloud regions, most of the water ice mantles are above this limit for the bulk of the cosmic rays.
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Dartois, E., Chabot, M., Id Barkach, T., Rothard, H., Augé, B., Agnihotri, A. N., Domaracka, A., & Boduch, P. (2018). Cosmic ray sputtering yield of interstellar H2O ice mantles. A&A, 618.
Résumé: Aims. Interstellar grain mantles present in dense interstellar clouds are in constant exchange with the gas phase via accretion and desorption mechanisms such as UV, X-ray photodesorption, cosmic ray induced sputtering, grain thermal fluctuations, and chemical reaction energy release. The relative importance of the various desorption mechanisms is of uttermost importance for astrophysical models to constrain the chemical evolution in such high density dense cloud regions.
Methods. The sputtering yields for swift ions simulating the effects of cosmic rays are most often measured in the semi-infinite limit using thick ice targets with the determination of the effective yield per incident ion. In this experimental work we investigated the sputtering yield as a function of ice mantle thickness, exposed to Xe ions at 95 MeV. The ion induced ice phase transformation and the sputtering yield were simultaneously monitored by infrared spectroscopy and mass spectrometry.
Results. The sputtering yield is constant above a characteristic ice layer thickness and then starts to decrease below this thickness. An estimate of the typical sputtering depth corresponding to this length can be evaluated by comparing the infinite thickness yield to the column density where the onset of the sputtering yield decrease occurs. In these experiments the measured characteristic desorption depth corresponds to ≈30 ice layers. Assuming an effective cylindrical shape for the volume of sputtered molecules, the aspect ratio is close to unity; in the semi-infinite ice film case this ratio is the diameter to height of the cylinder. This result shows that most ejected molecules arise from a rather compact volume. The measured infinite thickness sputtering yield for water ice mantles scales as the square of the ion electronic stopping power (Se, deposited energy per unit path length). Considering the experiments on insulators, we expect that the desorption depth dependence varies with Seα, where α ~ 1. Astrophysical models should take into account the thickness dependence constraints of these ice mantles in the interface regions when ices are close to their extinction threshold. In the very dense cloud regions, most of the water ice mantles are above this limit for the bulk of the cosmic rays.
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Dartois, E., Engrand, C., Duprat, J., Godard, M., Charon, E., Delauche, L., Sandt, C., & Borondics, F. (2018). Dome C ultracarbonaceous Antarctic micrometeorites. A&A, 609.
Résumé: Context. UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs) represent a small fraction of interplanetary dust particles reaching the Earth’s surface and contain large amounts of an organic component not found elsewhere. They are most probably sampling a contribution from the outer regions of the solar system to the local interplanetary dust particle (IDP) flux.
Aims. We characterize UCAMMs composition focusing on the organic matter, and compare the results to the insoluble organic matter (IOM) from primitive meteorites, IDPs, and the Earth.
Methods. We acquired synchrotron infrared microspectroscopy (μFTIR) and μRaman spectra of eight UCAMMs from the Concordia/CSNSM collection, as well as N/C atomic ratios determined with an electron microprobe.
Results. The spectra are dominated by an organic component with a low aliphatic CH versus aromatic C=C ratio, and a higher nitrogen fraction and lower oxygen fraction compared to carbonaceous chondrites and IDPs. The UCAMMs carbonyl absorption band is in agreement with a ketone or aldehyde functional group. Some of the IR and Raman spectra show a C≡N band corresponding to a nitrile. The absorption band profile from 1400 to 1100 cm-1 is compatible with the presence of C-N bondings in the carbonaceous network, and is spectrally different from that reported in meteorite IOM. We confirm that the silicate-to-carbon content in UCAMMs is well below that reported in IDPs and meteorites. Together with the high nitrogen abundance relative to carbon building the organic matter matrix, the most likely scenario for the formation of UCAMMs occurs via physicochemical mechanisms taking place in a cold nitrogen rich environment, like the surface of icy parent bodies in the outer solar system. The composition of UCAMMs provides an additional hint of the presence of a heliocentric positive gradient in the C/Si and N/C abundance ratios in the solar system protoplanetary disc evolution.
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Devolder, A., Luc-Koenig, E., Atabek, O., Desouter-Lecomte, M., & Dulieu, O. (2018). Proposal for the formation of ultracold deeply bound RbSr dipolar molecules by all-optical methods. Phys. Rev. A, 98(5), 053411.
Résumé: Ultracold paramagnetic and polar diatomic molecules are among the promising systems for quantum simulation of lattice-spin models. Unfortunately, their experimental observation is still challenging. Based on our recent ab initio calculations, we analyze the feasibility of all-optical schemes for the formation of ultracold 87Rb84Sr bosonic molecules. A first possibility is photoassociation followed by spontaneous emission. The photoassociation rate coefficients toward electronic states converging to the 87Rb(5s2S1/2)+84Sr(5s5p3P0,1,2) asymptotes are particularly small for vibrational levels close to the asymptote. The creation of molecules would be more interesting by using deeply bound levels which preferentially relax to the v''=0 level of the ground state. On the other hand, the photoassociation rate coefficients toward electronic states correlated to the Rb(5p2P1/2,3/2)+Sr(5s21S0) are significant for levels close to the asymptote. The spontaneous emission thus creates weakly bound molecules in a single vibrational level. A second option relies on stimulated Raman adiabatic passage implemented in a tight optical trap. It efficiently creates weakly bound ground-state molecules in a well-defined level, thus providing a promising alternative to magnetic Feshbach resonances for further population transfer toward the absolute ground state of the RbSr molecule.
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F Calvo and P Parneix and C Falvo. (2018). Atomistic modeling of the infrared response of fullerenes under hydrostatic pressure. Journal of Physics: Condensed Matter, 30(47), 474001.
Résumé: The anharmonic infrared spectrum of individual C 60 and C 70 fullerenes under hydrostatic pressure was theoretically computed by means of atomistic simulations. Using a tight-binding model for the fullerenes and a simple particle-based pressure-transmitting fluid, the structural and vibrational properties were determined at room temperature and up to 20 GPa. All properties generally exhibit relative variations that are linear with increasing pressure, but whose magnitude can be comparable to pure thermal effects. The bond length contraction usually agrees with existing results, and for C 70 our approach manages to reproduce the occasionally negative pressure coefficient found for some low-frequency modes in experiments.
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Falvo, C. (2018). Linear and non-linear infrared response of one-dimensional vibrational Holstein polarons in the anti-adiabatic limit: Optical and acoustical phonon models. The Journal of Chemical Physics, 148(7), 074103.
Résumé: The theory of linear and non-linear infrared response of vibrational Holstein polarons in one-dimensional lattices is presented in order to identify the spectral signatures of self-trapping phenomena. Using a canonical transformation, the optical response is computed from the small polaron point of view which is valid in the anti-adiabatic limit. Two types of phonon baths are considered: optical phonons and acoustical phonons, and simple expressions are derived for the infrared response. It is shown that for the case of optical phonons, the linear response can directly probe the polaron density of states. The model is used to interpret the experimental spectrum of crystalline acetanilide in the C=O range. For the case of acoustical phonons, it is shown that two bound states can be observed in the two-dimensional infrared spectrum at low temperature. At high temperature, analysis of the time-dependence of the two-dimensional infrared spectrum indicates that bath mediated correlations slow down spectral diffusion. The model is used to interpret the experimental linear-spectroscopy of model α-helix and β-sheet polypeptides. This work shows that the Davydov Hamiltonian cannot explain the observations in the NH stretching range.
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Falvo, C., Gamboa-Suárez, A., Cazayus-Claverie, S., Parneix, P., & Calvo, F. (2018). Isomerization kinetics of flexible molecules in the gas phase: Atomistic versus coarse-grained sampling. The Journal of Chemical Physics, 149(7), 072334.
Résumé: Isomerization kinetics of molecules in the gas phase naturally falls on the microcanonical ensemble of statistical mechanics, which for small systems might significantly differ from the more traditional canonical ensemble. In this work, we explore the examples of cis-trans isomerization in butane and bibenzyl and to what extent the fully atomistic rate constants in isolated molecules can be reproduced by coarse-graining the system into a lower dimensional potential of mean force (PMF) along a reaction coordinate of interest, the orthogonal degrees of freedom acting as a canonical bath in a Langevin description. Time independent microcanonical rate constants can be properly defined from appropriate state residence time correlation functions; however, the resulting rate constants acquire some time dependence upon canonical averaging of initial conditions. Stationary rate constants are recovered once the molecule is placed into a real condensed environment pertaining to the canonical ensemble. The effective one-dimensional kinetics along the PMF, based on appropriately chosen inertia and damping parameters, quantitatively reproduces the atomistic rate constants at short times but deviates systematically over long times owing to the neglect of some couplings between the system and the bath that are all intrinsically present in the atomistic treatment. In bibenzyl, where stronger temperature effects are noted than in butane, the effective Langevin dynamics along the PMF still performs well at short times, indicating the potential interest of this extremely simplified approach for sampling high-dimensional energy surfaces and evaluating reaction rate constants.
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Floß, J., Boulet, C., Hartmann, J. - M., Milner, A. A., & Milner, V. (2018). Electronic spin polarization with an optical centrifuge. Physical Review A, 98(4), 043401.
Résumé: We investigate, both theoretically and experimentally, the mechanism behind the creation of a macroscopic magnetization in a gas of paramagnetic molecules with an optical centrifuge, reported in [Phys. Rev. Lett. 118, 243201 (2017)]. Our analysis shows that the centrifuged super-rotors and noncentrifuged molecules are polarized in opposite directions, while the net magnetic moment of the whole ensemble at the end of the interaction with the laser pulse remains close to zero. As the super-rotors are more stable against reorienting collisions, their spin polarization, which points along the centrifuge axis, decays more slowly than the oppositely oriented polarization of the noncentrifuged molecules. The latter lose their directional rotation much more quickly and with it the polarization of their electronic spin. We show numerically that owing to this difference in decay rates, a net magnetization in the direction of the centrifuge is generated. The proposed model is supported by experimental data.
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Garcia, G. A., Gans, B., Kruger, J., Holzmeier, F., Roder, A., Lopes, A., Fittschen, C., Alcaraz, C., & Loison, J. - C. (2018). Valence shell threshold photoelectron spectroscopy of C3Hx (x = 0-3). Phys. Chem. Chem. Phys., 20, 8707–8718.
Résumé: We present the photoelectron spectra of C3Hx (x = 0-3) formed in a microwave discharge flow-tube reactor by consecutive H abstractions from C3H4 (C3Hx + F [rightward arrow] C3Hx-1 + HF (x = 1-4)), but also from F + CH4 schemes by secondary reactions. The spectra were obtained combining tunable VUV synchrotron radiation with double imaging electron/ion coincidence techniques, yielding mass-selected threshold photoelectron spectra. The obtained results complement not only existing ones, but for the first time the photoelectron spectra of C3, cyclic and linear C3H (c,l-C3H) as well as of the excited states of C3H3 are reported. In the case of c-C3H, l,t-C3H2 and C3H3, Franck-Condon simulations have been performed in order to assign the vibrational structure. The adiabatic ionization energies of these radicals are reported and compared to ab initio calculated values as well as to theoretical values using known enthalpies of formation.
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Gatti, F. (2018). Molecular dynamics simulated by photons. Nature, 557, 641.
Résumé: The microscopic behaviour of molecules can be difficult to model using ordinary computers because it is governed by quantum physics. A photonic chip provides a versatile platform for simulating such behaviour.
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Ghalgaoui, A., Horchani, R., Wang, J., Ouvrard, A., Carrez, S., & Bourguignon, B. (2018). Identification of active sites in oxidation reaction from real-time probing of adsorbate motion over Pd nanoparticles. J. Phys. Chem. Lett., 9(18), 5202–5206.
Résumé: Obtaining insight into the type of surface sites involved in a reaction is essential to understand catalytic mechanisms at the atomic level and a key for understanding selectivity in surface-catalyzed reactions. Here we use ultrafast broad-band vibrational spectroscopy to follow in real-time diffusion of CO molecules over a palladium nanoparticle surface toward an active site. Site-to-site hopping is triggered by laser excitation of electrons and followed in real-time from subpicosecond changes in the vibrational spectra. CO photoexcitation occurs in 400 fs and hopping from NP facets to edges follows within ∼1 ps. Kinetic modeling allows to quantify the contribution of different facet sites to the catalytic reaction. These results provide useful insights for understanding the mechanism of chemical reactions catalyzed by metal NPs.
Supporting Information
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Gutierrez-Quintanilla, A., Briant M, Mengesha, E., Gaveau MA, Mestdagh, J. - M., Soep B, Crepin, C., & Poisson L. (2018). A HElium NanoDroplet Isolation (HENDI) investigation of the weak hydrogen bonding in the propyne dimer (CH3CCH)2. Phys Chem Chem Phys, 20, 28658.
Résumé: A HElium Nanodroplet Isolation (HENDI) experiment was performed to explore the absorption spectra of the propyne monomer (CH3CCH), dimer and (CH3CCH)>/=3 multimers in the vicinity of the CH stretch region nu1 of the monomer. Ab initio calculations were performed at the MP2 level to document the potential energy surface of the dimer. This provided the necessary parameters to simulate the absorption spectrum of the dimer and thus facilitate the interpretation of the experiment. The central result was to observe three isomers of the dimer, hence reflecting the complexity of the weak CHpi H-bonding when several H-donors are at play.
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Gutierrez-Quintanilla, A., Chevalier M, Ceponkus, J., Lozada-Garcia RR, Mestdagh, J. - M., & Crepin C. (2018). Large amplitude motions within molecules trapped in solid parahydrogen. Faraday Discuss, 212, 499–515.
Résumé: Molecules of the beta-diketone and beta-dialdehyde families were trapped in solid parahydrogen (pH2) to investigate the vibrational behavior of systems containing an intramolecular hydrogen bond (IHB). In the simplest beta-diketone, acetylacetone (AcAc), H transfer related to the IHB is coupled with methyl torsions. In pH2, the study of nuclear spin conversion (NSC) in methyl groups allows the characterisation of the influence of these large amplitude motions on the vibrational modes. The deuteration of the OH group involved in the IHB has important consequences on the vibrational spectrum of the molecule and evidence of NSC in methyl groups is difficult to obtain. In the chlorine derivative (3-chloroacetylacetone), the H-transfer is no longer coupled with methyl torsion, and NSC has undetectable effects on the IR spectrum. A search of H tunnelling splitting in the IR spectra of beta-dialdehydes trapped in pH2 was performed. A few modes of 2-chloromalonaldehyde appear as doublets and were assigned to tunnelling levels. The spectroscopic results related to large amplitude motions are detailed and discussed, highlighting puzzling effects.
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Gutierrez-Quintanilla, A., Chevalier M, Platakyte, R., Ceponkus J, Rojas-Lorenzo, G. A., & Crepin C. (2018). 2-Chloromalonaldehyde, a model system of resonance-assisted hydrogen bonding: vibrational investigation. Phys Chem Chem Phys, 20, 12888.
Résumé: The chelated enol isomer of 2-chloromalonaldehyde (2-ClMA) is experimentally characterized for the first time by IR and Raman spectroscopies. The spectra are obtained by trapping the molecule in cryogenic matrices and analyzed with the assistance of theoretical calculations. Experiments were performed in argon, neon and para-hydrogen matrices. The results highlight puzzling matrix effects, beyond site effects, which are interpreted as due to a tunneling splitting of the vibrational levels related to the proton transfer along the internal hydrogen bond (IHB). 2-ClMA is thus one of the very few molecules in which the H tunneling has been observed in cryogenic matrices. The comparison with its parent molecule (malonaldehyde) shows experimentally and theoretically the weakening of the IHB upon chlorination, with a reduced cooperative effect in the resonance assisted hydrogen bond. In addition, the Cl substitution induces an important stabilization of two open enol conformers. These two open forms appear in the spectra of as-deposited samples, meaning that, in contrast with other well-studied molecules of the same family (beta-dialdehydes and beta-diketones), they are present in the gas phase at room temperature.
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Ha-Thi, M. - H., Pham, V. - T., Pino, T., Maslova, V., Quaranta, A., Lefumeux, C., Leiblc, W., & and Aukauloo, A. (2018). Photoinduced electron transfer in a molecular dyad by nanosecond pump–pump–probe spectroscopy. Photochem. Photobiol. Sci., 17, 903–909.
Résumé: The design of robust and inexpensive molecular photocatalysts for the conversion of abundant stable molecules like H2O and CO2 into an energetic carrier is one of the major fundamental questions for scientists nowadays. The outstanding challenge is to couple single photoinduced charge separation events with the sequential accumulation of redox equivalents at the catalytic unit for performing multielectronic catalytic reactions. Herein, double excitation by nanosecond pump–pump–probe experiments was used to interrogate the photoinduced charge transfer and charge accumulation on a molecular dyad composed of a porphyrin chromophore and a ruthenium-based catalyst in the presence of a reversible electron acceptor. An accumulative charge transfer state is unattainable because of rapid reverse electron transfer to the photosensitizer upon the second excitation and the low driving force of the forward photodriven electron transfer reaction. Such a method allows the fundamental understanding of the relaxation mechanism after two sequential photon absorptions, deciphering the undesired electron transfer reactions that limit the charge accumulation efficiency. This study is a step toward the improvement of synthetic strategies of molecular photocatalysts for light-induced charge accumulation and more generally, for solar energy conversion.
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Hartmann, J. - M., Boulet, C., Tran, D. D., Tran, H., & Baranov, Y. (2018). Effect of humidity on the absorption continua of CO2 and N2 near 4 μm: Calculations, comparisons with measurements, and consequences for atmospheric spectra. Journal of Chemical Physics, 148(5), 054304.
Résumé: We present a theoretical study of the effects of collisions with water vapor molecules on the absorption, around 4 μm, in both the high frequency wing of the CO2 ν3 band and the collision-induced fundamental band of N2. Calculations are made for the very first time, showing that predictions based on classical molecular dynamics simulations enable, without adjustment of any parameter, very satisfactory agreement with the few available experimental determinations. This opens the route for a future study in which accurate temperature-dependent (semi-empirical) models will be built and checked through comparisons between computed and measured atmospheric spectra. This is of interest since, as demonstrated by simulations, neglecting the humidity of air can lead to significant modifications of the atmospheric transmission (and thus also emission) between 2000 and 2800 cm−1.
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Hartmann, J. - M., Boulet, C., Zhang, H., Billard, F., Faucher, O., & Lavorel, B. (2018). Collisional dissipation of the laser-induced alignment of ethane gas: A requantized classical model. The Journal of Chemical Physics, 149(15), 154301.
Résumé: We present the first theoretical study of collisional dissipation of the alignment of a symmetric-top molecule (ethane gas) impulsively induced by a linearly polarized non-resonant laser field. For this, Classical Molecular Dynamics Simulations (CMDSs) are carried out for an ensemble of C2H6 molecules based on knowledge of the laser-pulse characteristics and on an input intermolecular potential. These provide, for a given gas pressure and initial temperature, the orientations of all molecules at all times from which the alignment factor is directly obtained. Comparisons with measurements show that these CMDSs well predict the permanent alignment induced by the laser pulse and its decay with time but, as expected, fail in generating alignment revivals. However, it is shown that introducing a simple requantization procedure in the CMDS “creates” these revivals and that their predicted dissipation decay agrees very well with measured values. The calculations also confirm that, as for linear molecules, the permanent alignment of ethane decays more slowly than the transient revivals. The influence of the intermolecular potential is studied as well as that of the degree of freedom associated with the molecular rotation around the symmetry axis. This reveals that ethane practically behaves as a linear molecule because the intermolecular potential is only weakly sensitive to rotation around the C–C axis.
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Hartmann, J. - M., Boulet, C., Zhang, H., Billard, F., Faucher, O., & Lavorel, B. (2018). Collisional dissipation of the laser-induced alignment of ethane gas: Energy corrected sudden quantum model. The Journal of Chemical Physics, 149(21), 214305.
Résumé: We present the first quantum mechanical model of the collisional dissipation of the alignment of a gas of symmetric-top molecules (ethane) impulsively induced by a linearly polarized non-resonant laser field. The approach is based on use of the Bloch model and of the Markov and secular approximations in which the effects of collisions are taken into account through the state-to-state rates associated with exchanges among the various rotational states. These rates are constructed using the Energy Corrected Sudden (ECS) approximation with (a few) input parameters obtained independently from fits of the pressure-broadening coefficients of ethane absorption lines. Based on knowledge of the laser pulse characteristics and on these rates, the time-dependent equation driving the evolution of the density matrix during and after the laser pulse is solved and the time dependence of the so-called “alignment factor” is computed. Comparisons with measurements, free of any adjusted parameter, show that the proposed approach leads to good agreement with measurements. The analysis of the ECS state-to-state collisional rates demonstrates that, as in the case of linear molecules, collision-induced changes of the rotational angular momentum orientation are slower than those of its magnitude. This explains why the collisional decay of the permanent component of the alignment is significantly slower than that of the amplitudes of the transient revivals in both experimental and computed results. It is also shown that, since intermolecular forces within C2H6 colliding pairs weakly depend on rotations of the molecules around their C–C bond, the dissipation mechanism of the alignment in pure ethane is close to that involved in linear molecules.
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Hartmann, J. - M., Tran, H., Armante, R., Boulet, C., Campargue, A., Forget, F., Gianfrani, L., Gordon, I., Guerlet, S., Gustafsson, M., Hodges, J. T., Kassi, S., Lisak, D., Thibault, F., & Toon, G. C. (2018). Recent advances in collisional effects on spectra of molecular gases and their practical consequences. Journal of Quantitative Spectroscopy and Radiative Transfer, 213, 178–227.
Résumé: We review progress, since publication of the book “Collisional effects on molecular spectra: Laboratory experiments and models, consequences for applications” (Elsevier, Amsterdam, 2008), on measuring, modeling and predicting the influence of pressure (ie of intermolecular collisions) on the spectra of gas molecules. We first introduce recently developed experimental techniques of high accuracy and sensitivity. We then complement the above mentioned book by presenting the theoretical approaches, results and data proposed (mostly) in the last decade on the topics of isolated line shapes, line-broadening and -shifting, line-mixing, the far wings and associated continua, and collision-induced absorption. Examples of recently demonstrated consequences of the progress in the description of spectral shapes for some practical applications (metrology, probing of gas media, climate predictions) are then given. Remaining issues and directions for future research are finally discussed.
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Heays, A. N., de Oliveira, N., Gans, B., Ito, K., Boyé-Péronne, S., Douin, S., Hickson, K. M., Nahon, L., & and Loison, J. C. (2018). High-resolution one-photon absorption spectroscopy of the D 2S- <- X 2Pi system of radical OH and OD. Journal of Quantitative Spectroscopy and Radiative Transfer, 204, 12–22.
Résumé: Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the A(v=0) <-X(v=0), D(v=0)<-X(v=0) and D(v=1) <-X(v=0) bands of the OH and OD radicals generated in a plasma-discharge source using synchrotron radiation as a background continuum coupled with the VUV Fourier-transform spectrometer on the DESIRS beamline of synchrotron SOLEIL. High-resolution spectra permitted the quantification of transition frequencies, relative f-values, and natural line broadening. The f -values were absolutely calibrated with respect to a previous measurement of A(v=0) <-X(v=0) [C. C. Wang, D. K. Killinger, Effect of rotational excitation on the band oscillator strength of OH, Phys. Rev. A 20 (1979) 1495–1498.]. Lifetime broadening of the excited D(v=0) and D(v=1) levels is measured for the first time and compared with previous experimental limits, and implies a lifetime 5 times shorter than a theoretical prediction [M. P. J. van der Loo, G. C. Groenenboom, Ab initio calculation of (2+1)
resonance enhanced multiphoton ionization spectra and lifetimes of the (D,3) states of OH and OD, J. Chem. Phys. 123 (7) (2005) 074310.]. A local perturbation of the D(v=0) level in OH was found.
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Holzmeier, F., Bello, R. Y., Herve, M., Achner, A., Baumann, T. M., Meyer, M., Finetti, P., Di Fraia, M., Gauthier, D., Roussel, E., Plekan, O., Richter, R., Prince, K. C., Callegari, C., Bachau, H., Palacios, A., Martin, F., & Dowek, D. (2018). Control of H2 Dissociative Ionization in the Nonlinear Regime Using Vacuum Ultraviolet Free-Electron Laser Pulses. Phys Rev Lett, 121(10), 103002.
Résumé: The role of the nuclear degrees of freedom in nonlinear two-photon single ionization of H_{2} molecules interacting with short and intense vacuum ultraviolet pulses is investigated, both experimentally and theoretically, by selecting single resonant vibronic intermediate neutral states. This high selectivity relies on the narrow bandwidth and tunability of the pulses generated at the FERMI free-electron laser. A sustained enhancement of dissociative ionization, which even exceeds nondissociative ionization, is observed and controlled as one selects progressively higher vibronic states. With the help of ab initio calculations for increasing pulse durations, the photoelectron and ion energy spectra obtained with velocity map imaging allow us to identify new photoionization pathways. With pulses of the order of 100 fs, the experiment probes a timescale that lies between that of ultrafast dynamical processes and that of steady state excitations.
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IdBarkach, T., Mahajan, T., Chabot, M., Béroff, K., Aguirre, N. F., Diaz-Tendero, S., Launoy, T., Padellec, A. L., Perrot, L., Bonnin, M. A., Le, K. C., Geslin, F., de Séréville, N., Hammache, F., Jallat, A., Meyer, A., Charon, E., Pino, T., Hamelin, T., & Wakelam, V. (2018). Semiempirical breakdown curves of C2N(+) and C3N(+) molecules; application to products branching ratios predictions of physical and chemical processes involving these adducts. Molecular Astrophysics, 12, 25–32.
Résumé: We constructed semiempirical breakdown curves (BDC) for C2N, C3N, C2N+ and C3N+ molecules. These BDC, which are energy dependent dissociation branching ratios (BR) curves, were used to predict products branching ratios for various processes leading to the formation of C2N(+) and C3N(+) excited adducts. These processes, of astrochemical interest, are neutral-neutral and ion-molecule reactions, dissociative recombination and charge transfer reactions with He+. Model predictions of BR are compared to the literature data and to reported values in the kinetic database for astrochemistry KIDA. With the new BR values, the CnN abundances in cold cores were simulated.
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Joost, M., Nava, M., Transue, W. J., Martin-Drumel, M. - A., McCarthy, M. C., Patterson, D., & Cummins, C. C. (2018). Sulfur monoxide thermal release from an anthracene-based precursor, spectroscopic identification, and transfer reactivity. Proc Natl Acad Sci USA, 115(23), 5866–5871.
Résumé: The generation of highly reactive molecules under controlled conditions is desirable, as it allows exploration of synthetic chemistry and enables spectroscopic studies of such elusive species. We report here on the synthesis and reactivity of a precursor molecule that readily fragments with concomitant expulsion of dinitrogen and anthracene to release the highly reactive sulfur monoxide, a compound of interest for both synthetic chemists and astrochemists.Sulfur monoxide (SO) is a highly reactive molecule and thus, eludes bulk isolation. We report here on synthesis and reactivity of a molecular precursor for SO generation, namely 7-sulfinylamino-7-azadibenzonorbornadiene (1). This compound has been shown to fragment readily driven by dinitrogen expulsion and anthracene formation on heating in the solid state and in solution, releasing SO at mild temperatures (<100 °C). The generated SO was detected in the gas phase by MS and rotational spectroscopy. In solution, 1 allows for SO transfer to organic molecules as well as transition metal complexes.
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Kalashnyk, N., Amiaud, L., Dablemont, C., Lafosse, A., Bobrov, K., & Guillemot, L. (2018). Strain relaxation and epitaxial relationship of perylene overlayer on Ag(110). The Journal of Chemical Physics, 148(21), 214702.
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Kennedy, E. T., Mosnier, J. - P., van Kampen, P., Bizau, J. - M., Cubaynes, D., Guilbaud, S., Carniato, S., Puglisi, A., & Sisourat, N. (2018). Evolution of L-shell photoabsorption of the molecular-ion series SiH_n^+(n=1,2,3): Experimental and theoretical studies. Phys. Rev. A, 97(4), 043410.
Résumé: We report on complementary laboratory and theoretical investigations of the 2p photoexcitation cross sections for the molecular-ion series SiHn+ (n=1,2,3) near the L-shell threshold. The experiments used an electron cyclotron resonance (ECR) plasma molecular-ion source coupled with monochromatized synchrotron radiation in a merged-beam configuration. For all three molecular ions, the Si2+ decay channel appeared dominant, suggesting similar electronic and nuclear relaxation patterns involving resonant Auger and dissociation processes, respectively. The total yields of the Si2+ products were recorded and put on absolute cross-section scales by comparison with the spectrum of the Si+ parent atomic ion. Interpretation of the experimental spectra ensued from a comparison with total photoabsorption cross-sectional profiles calculated using ab initio configuration interaction theoretical methods inclusive of vibrational dynamics and contributions from inner-shell excitations in both ground and valence-excited electronic states. The spectra, while broadly similar for all three molecular ions, moved towards lower energies as the number of screening hydrogen atoms increased from one to three. They featured a wide and shallow region below ∼107eV due to 2p→σ∗ transitions to dissociative states, and intense and broadened peaks in the ∼107–113−eV region merging into sharp Rydberg series due to 2p→nδ,nπ transitions converging on the LII,III limits above ∼113eV. This overall spectral shape is broadly replicated by theory in each case, but the level of agreement does not extend to individual resonance structures. In addition to the fundamental interest, the work should also prove useful for the understanding and modeling of astronomical and laboratory plasma sources where silicon hydride molecular species play significant roles.
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Kölsch, S., Fritz, F., Fenner, M.A., Kurch, S., Wöhrl, N., Mayne, A.J., Dujardin, G. & Meyer, C. (2018). Kelvin probe force microscopy studies of the charge effects upon adsorption of carbon nanotubes and C60 fullerenes on hydrogen-terminated diamond. J. Appl. Phys., 123(1), 15103.
Résumé: Hydrogen-terminated diamond is known for its unusually high surface conductivity that is ascribed to its negative electron affinity. In the presence of acceptor molecules, electrons are expected to transfer from the surface to the acceptor, resulting in p-type surface conductivity. Here, we present Kelvin probe force microscopy (KPFM) measurements on carbon nanotubes and C60 adsorbed onto a hydrogen-terminated diamond(001) surface. A clear reduction in the Kelvin signal is observed at the position of the carbon nanotubes and C60 molecules as compared with the bare, air-exposed surface. This result can be explained by the high positive electron affinity of carbon nanotubes and C60, resulting in electron transfer from the surface to the adsorbates. When an oxygen-terminated diamond(001) is used instead, no reduction in the Kelvin signal is obtained. While the presence of a charged adsorbate or a difference in work function could induce a change in the KPFM signal, a charge transfer effect of the hydrogen-terminated diamond surface, by the adsorption of the carbon nanotubes and the C60 fullerenes, is consistent with previous theoretical studies.
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Kuncic, Z., & Lacombe, S. (2018). Nanoparticle radio-enhancement: principles, progress and application to cancer treatment. Physics In Medicine And Biology, 63(2).
Résumé: Enhancement of radiation effects by high-atomic number nanoparticles (NPs) has been increasingly studied for its potential to improve radiotherapeutic efficacy. The underlying principle of NP radio-enhancement is the potential to release copious electrons into a nanoscale volume, thereby amplifying radiation-induced biological damage. While the vast majority of studies to date have focused on gold nanoparticles with photon radiation, an increasing number of experimental, theoretical and simulation studies have explored opportunities offered by other NPs (e.g. gadolinium, platinum, iron oxide, hafnium) and other therapeutic radiation sources such as ion beams. It is thus of interest to the research community to consolidate findings from the different studies and summarise progress to date, as well as to identify strategies that offer promising opportunities for clinical translation. This is the purpose of this Topical Review.
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Le Barbu-Debus, K., Scherrer, A., Bouchet, A., Sebastiani, D., Vuilleumier, R., & Zehnacker, A. (2018). Effect of puckering motion and hydrogen bond formation on the vibrational circular dichroism spectrum of a flexible molecule: the case of (S)-1-indanol. Phys Chem Chem Phys, 20(21), 14635–14646.
Résumé: The influence of flexibility and hydrogen bond formation on the IR absorption and vibrational circular dichroism (VCD) spectrum of a floppy protic molecule, namely, (S)-1-indanol, is studied in both non-polar CCl4 and polar DMSO solvents. The experimental IR absorption and VCD spectra obtained by Fourier transform spectroscopy are interpreted using both static density functional theory (DFT) calculations and first principles molecular dynamics (FPMD) within DFT, using the nuclear velocity perturbation theory (NVPT). Simulation of the spectra based on static optimised geometries is not sufficient in CCl4 and going beyond static calculations is mandatory for satisfactorily reproducing the VCD spectra. The FPMD results obtained in DMSO indicate that (S)-1-indanol is hydrogen-bonded to one DMSO molecule. As a result, static “cluster-in-the-bulk” DFT calculations in which the solute-solvent interaction is modeled as the most stable (S)-1-indanol:DMSO complexes in a DMSO continuum yield satisfactory agreement with the experiment. Correspondence between experimental and simulated spectra is slightly improved when the VCD spectrum is calculated as the summed contributions of snapshots extracted from FPMD trajectories, due to better sampling of the potential-energy surface. Finally, NVPT calculations further improve the description of experimental spectra by taking into account higher-energy structures, which are not necessary local minima.
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Lee, K. L. K., Martin-Drumel, M. - A., Lattanzi, V., McGuire, B. A., Caselli, P., & McCarthy, M. C. (2018). Gas phase detection and rotational spectroscopy of ethynethiol, HCCSH. Molecular Physics, , 1–11.
Résumé: We report the gas-phase detection and spectroscopic characterisation of ethynethiol , a metastable isomer of thioketene using a combination of Fourier-transform microwave and submillimetre-wave spectroscopies. Several a-type transitions of the normal species were initially detected below 40 GHz using a supersonic expansion-electrical discharge source, and subsequent measurement of higher-frequency, b-type lines using double resonance provided accurate predictions in the submillimetre region. With these, searches using a millimetre-wave absorption spectrometer equipped with a radio frequency discharge source were conducted in the range 280-660 GHz, ultimately yielding nearly 100 transitions up to ^rRo(36) and rQo(36). From the combined data set, all three rotational constants and centrifugal distortion terms up to the sextic order were determined to high accuracy, providing a reliable set of frequency predictions to the lower end of the THz band. Isotopic substitution has enabled both a determination of the molecular structure of HCCSH and, by inference, its formation pathway in our nozzle discharge source via the bimolecular radical-radical recombination reaction , which is calculated to be highly exothermic (-477 kJ/mol) using the HEAT345(Q) thermochemical scheme.
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Liao, Y. Y., Melissen, S. T. A. G., Audibert, J. F., Vu, T. T., Clavier, G., Meallet-Renault, R., Retailleau, P., Lemaistre, J. P., Genot, V., & Pansu, R. (2018). Fluorescence Spectroscopy of AdamBODIPY Single Crystals. Chemphotochem, 2(2), 72–80.
Résumé: Interest in the fluorescence of organic solids is increasing with the development of nanosensors and research into new molecules with aggregation-induced fluorescence properties. We have gone beyond the qualitative observation of fluorescence by analyzing the luminescence properties of planar single crystals of a 4,4'-difluoro-4-bora-(3a,4a)-diaza-s-indacene (BODIPY) derivative with micrometric dimensions. A simple Frenkel exciton model applied to this crystal predicts one band. From time-resolved fluorescence spectra, three emissions were distinguished. The shortest-lived one at lambda = 547 nm was predicted by theory and corresponds to an exciton lifetime of 0.9 ns. A trap with an intermediate emission lifetime of 1.2 ns was found at 569 nm and a final trap at 620 nm has a lifetime of 1.9 ns. These attributions were confirmed by the study of the polarization of these emissions. The 547 nm emission was polarized along the long axis of the crystal as predicted by the Frenkel exciton model. The 569 nm emission was polarized perpendicularly to the plane of the crystal and the 620 nm emission was polarized along the short axis. Thus, the two red-shifted bands were related to well-defined defects with specific orientations in the crystal. Fluorescence lifetime imaging measurements showed that the density of these defects is not uniform and that under our synthesis conditions, they are formed in the initial steps of the growth and therefore appear in the center of the crystals.
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Mangaud E., P. - J. R., Sugny D., Meier C., Atabek O, & Desouter-Lecomte M. (2018). Non-Markovianity in the optimal control of an open quantum system described by hierarchical equations of motion. New J. Phys., 20, 043050.
Résumé: Optimal control theory is implemented with fully converged hierarchical equations of motion (HEOM) describing the time evolution of an open system density matrix strongly coupled to the bath in a spin-boson model. The populations of the two-level sub-system are taken as control objectives; namely, their revivals or exchange when switching off the field. We, in parallel, analyze how the optimal electric field consequently modifies the information back flow from the environment through different non-Markovian witnesses. Although the control field has a dipole interaction with the central sub-system only, its indirect influence on the bath collective mode dynamics is probed through HEOM auxiliary matrices, revealing a strong correlation between control and dissipation during a non-Markovian process. A heterojunction is taken as an illustrative example for modeling in a realistic way the two-level sub-system parameters and its spectral density function leading to a non-perturbative strong coupling regime with the bath. Although, due to strong system-bath couplings, control performances remain rather modest, the most important result is a noticeable increase of the non-Markovian bath response induced by the optimally driven processes.
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Marinica, D. C., Silkin, V. M., Kazansky, A. K., & Borisov, A. G. (2018). Controlling gap plasmons with quantum resonances. Phys. Rev. B, 98(15), 155426.
Résumé: We use classical electrodynamics, time-dependent density functional theory, and random-phase approximation to study the gap plasmons propagating in the nm-wide gap between metal surfaces. Particular emphasis is given to the quantum effects emerging when the junction is functionalized with a nanostructure supporting unoccupied gap localized electronic states. With the example of a quantum well (QW) introduced in the junction we show that the optically assisted electron transport across the junction via the gateway QW localized electronic states might strongly affect the lifetime and the propagation length of the gap plasmon. The coupling to the single-particle electron-hole excitations from occupied electronic states at metal surfaces into the QW-localized electronic states provides an efficient decay channel of the gap plasmon mode. Different from the through-gap electron tunneling discussed in the plasmonics literature, the electron transport involving the gateway electronic state is characterized by the threshold behavior with plasmon frequency. As a consequence, the dynamics of the gap plasmon can be controlled by varying the binding energy of the QW-localized electronic state. In more general terms, our results demonstrate strong sensitivity of the gap plasmons to the optically assisted electron transport properties of the junction which opens further perspectives in design of nanosensors and integrated active optical devices.
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Mathieu, M. - C., Toullec, A., Benoit, C., Berry, R., Validire, P., Beaumel, P., Vincent, Y., Maroun, P., Vielh, P., Alchab, L., Farcy, R., Moniz-Koum, H., Fontaine-Aupart, M. - P., Delaloge, S., & Balleyguier, C. (2018). Preclinical ex vivo evaluation of the diagnostic performance of a new device for in situ label-free fluorescence spectral analysis of breast masses. European radiology, , 1–9.
Résumé: OBJECTIVES: To assess the diagnostic performance of a new device for in situ label-free fluorescence spectral analysis of breast masses in freshly removed surgical specimens, in preparation for its clinical development. METHODS: Sixty-four breast masses from consenting patients who had undergone either a lumpectomy or a mastectomy were included. Label-free fluorescence spectral acquisitions were obtained with a 25G fibre-containing needle inserted into the mass. Data from benign and malignant masses were compared to establish the most discriminating thresholds and measurement algorithms. Accuracy was verified using the bootstrap method. RESULTS: The final histological examination revealed 44 invasive carcinomas and 20 benign lesions. The maximum intensity of fluorescence signal was discriminant between benign and malignant masses (p < .0001) whatever their sizes. Statistical analysis indicated that choosing five random measurements per mass was the best compromise to obtain high sensitivity and high negative predictive value with the fewest measurements. Thus, malignant tumours were identified with a mean sensitivity, specificity, negative and positive predictive value of 98.8%, 85.4%, 97.2% and 93.5%, respectively. CONCLUSION: This new in situ tissue autofluorescence evaluation device allows accurate discrimination between benign and malignant breast masses and deserves clinical development. KEY POINTS: A new device allows in situ label-free fluorescence analysis of ex vivo breast masses Maximum fluorescence intensity discriminates benign from malignant masses (p < .0001) Five random measurements allow a high negative predictive value (97.2%).
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McGuire, B. A., Martin-Drumel, M. - A., Lee, K. L. K., Stanton, J. F., Gottlieb, C. A., & McCarthy, M. C. (2018). Vibrational satellites of C2S, C3S, and C4S: microwave spectral taxonomy as a stepping stone to the millimeter-wave band. Phys. Chem. Chem. Phys., 20(20), 13870–13889.
Résumé: We present a microwave spectral taxonomy study of several hydrocarbon/CS2 discharge mixtures in which more than 60 distinct chemical species, their more abundant isotopic species, and/or their vibrationally excited states were detected using chirped-pulse and cavity Fourier-transform microwave spectroscopies. Taken together, in excess of 85 unique variants were detected, including several new isotopic species and more than 25 new vibrationally excited states of C2S, C3S, and C4S, which have been assigned on the basis of published vibration-rotation interaction constants for C3S, or newly calculated ones for C2S and C4S. On the basis of these precise, low-frequency measurements, several vibrationally exited states of C2S and C3S were subsequently identified in archival millimeter-wave data in the 253-280 GHz frequency range, ultimately providing highly accurate catalogs for astronomical searches. As part of this work, formation pathways of the two smaller carbon-sulfur chains were investigated using 13C isotopic spectroscopy, as was their vibrational excitation. The present study illustrates the utility of microwave spectral taxonomy as a tool for complex mixture analysis, and as a powerful and convenient 'stepping stone' to higher frequency measurements in the millimeter and submillimeter bands.
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Meek, S. A., Hipke, A., Guelachvili, G., Hansch, T. W., & Picque, N. (2018). Doppler-free Fourier transform spectroscopy. Optics Letters, 43(1), 162–165.
Résumé: Sub-Doppler broadband multi-heterodyne spectroscopy is proposed and experimentally demonstrated. Using two laser frequency combs of slightly different repetition frequencies, we have recorded Doppler-free two-photon dual-comb spectra of atomic rubidium resonances of a width of 6 MHz, while simultaneously interrogating a spectral span of 10 THz. The atomic transitions are uniquely identified via the intensity modulation of the observed fluorescence radiation. To the best of our knowledge, these results represent the first demonstration of Doppler-free Fourier transform spectroscopy and extend the range of applications of broadband spectroscopy towards precision nonlinear spectroscopy. (C) 2017 Optical Society of America
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Mendive-Tapia, D., Mangaud, E., Firmino, T., de la Lande, A., Desouter-Lecomte, M., Meyer, H. D., & Gatti, F. (2018). Multidimensional Quantum Mechanical Modeling of Electron Transfer and Electronic Coherence in Plant Cryptochromes: The Role of Initial Bath Conditions. Journal Of Physical Chemistry B, 122(1), 126–136.
Résumé: A multidimensional quantum mechanical protocol is used to describe the photoinduced electron transfer and electronic coherence in plant cryptochromes without any semiempirical, e.g., experimentally obtained, parameters. Starting from a two-level spin-boson Hamiltonian we look at the effect that the initial photoinduced nuclear bath distribution has on an intermediate step of this biological electron transfer cascade for two idealized cases. The first assumes a slow equilibration of the nuclear bath with respect to the previous electron transfer step that leads to an ultrafast decay with little temperature dependence; while the second assumes a prior fast bath equilibration on the donor potential energy surface leading to a much slower decay, which contrarily displays a high temperature dependence and a better agreement with previous theoretical and experimental results. Beyond Marcus and semiclassical pictures these results unravel the strong impact that the presence or not of equilibrium initial conditions has on the electronic population and coherence dynamics at the quantum dynamics level in this and conceivably in other biological electron transfer cascades.
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Momeni, A., Staicu Casagrande, E. M., Dechaux, A., & Khemliche, H. (2018). Ultrafast Crystallization Dynamics at an Organic-Inorganic Interface Revealed in Real Time by Grazing Incidence Fast Atom Diffraction. J. Phys. Chem. Lett., 9(4), 908–913.
Résumé: The poor structural properties of organic-inorganic interfaces and their variability represent the main cause of device under-performance. Understanding and controlling the development of these properties in real time has been a difficult experimental challenge. Using a recent technique based on grazing incidence fast atom diffraction (GIFAD), we were able to directly observe during deposition structural transitions in a perylene monolayer on Ag(110). Crystallization from the liquid phase occurs into two distinct structures with drastically different dynamics. Transition to the most compact packing occurs by self-organization only after a second layer has started to build up; subsequent incorporation of molecules from second to first layer triggers an ultrafast crystallization on a macroscopic sale. The final compact crystalline structure shows a long-range order and superior stability, which opens good perspectives for producing in a controlled manner highly ordered hybrid interfaces for photovoltaics and molecular electronics.
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Morán, G., Ramos-Chagas, G., Hugelier, S., Xie, X., Boudjemaa, R., Ruckebusch, C., Sliwa, M., Darmanin, T., Gaucher, A., Prim, D., Godeau, G., Amigoni, S., Guittard, F., & Méallet-Renault, R. (2018). Superhydrophobic polypyrene films to prevent Staphylococcus aureus and Pseudomonas aeruginosa biofilm adhesion on surfaces: high efficiency deciphered by fluorescence microscopy. Photochem. Photobiol. Sci., 17(8), 1023–1035.
Résumé: A blue luminescent and superhydrophobic coating based on an electropolymerized fluorinated-pyrene monomer and its planktonic bacteria and biofilm repellent properties are reported. Two different pathogenic bacterial strains (Gram-positive and Gram-negative) at two different incubation times (2 h planktonic bacterial and 24 h biofilm adhesion) were studied and monitored (analyzed) using multicolor scanning confocal fluorescence microscopy. The coating was proved to reduce bacterial adhesion by 65%. It is highly effective against biofilm attachment, with 90% reduction of bacteria surface coverage. This blue fluorescent surface provides a facile method to characterize the coating, observe the bacterial distribution and quantify the bacterial coverage rate by fluorescence imaging of different colors. Furthermore, the film does not show significant bacterial toxicity during the working incubation times.
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Mulas, G., Falvo, C., Cassam-Chenaï, P., & Joblin, C. (2018). Anharmonic vibrational spectroscopy of polycyclic aromatic hydrocarbons (PAHs). The Journal of Chemical Physics, 149(14), 144102.
Résumé: While powerful techniques exist to accurately account for anharmonicity in vibrational molecular spectroscopy, they are computationally very expensive and cannot be routinely employed for large species and/or at non-zero vibrational temperatures. Motivated by the study of Polycyclic Aromatic Hydrocarbon (PAH) emission in space, we developed a new code, which takes into account all modes and can describe all infrared transitions including bands becoming active due to resonances as well as overtone, combination, and difference bands. In this article, we describe the methodology that was implemented and discuss how the main difficulties were overcome, so as to keep the problem tractable. Benchmarking with high-level calculations was performed on a small molecule. We carried out specific convergence tests on two prototypical PAHs, pyrene (C16H10) and coronene (C24H12), aiming at optimising tunable parameters to achieve both acceptable accuracy and computational costs for this class of molecules. We then report the results obtained at 0 K for pyrene and coronene, comparing the calculated spectra with available experimental data. The theoretical band positions were found to be significantly improved compared to harmonic density functional theory calculations. The band intensities are in reasonable agreement with experiments, the main limitation being the accuracy of the underlying calculations of the quartic force field. This is a first step toward calculating moderately high-temperature spectra of PAHs and other similarly rigid molecules using Monte Carlo sampling.
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Nieuwjaer, N., Desfrancois, C., Lecomte, F., Manil, B., Soorkia, S., Broquier, M., & Gregoire, G. (2018). Photodissociation Spectroscopy of Cold Protonated Synephrine: Surprising Differences between IR-UV Hole-Burning and IR Photodissociation Spectroscopy of the O-H and N-H Modes. J Phys Chem A, .
Résumé: We report the UV and IR photofragmentation spectroscopies of protonated synephrine in a cryogenically cooled Paul trap. Single (UV or IR) and double (UV-UV and IR-UV) resonance spectroscopies have been performed and compared to quantum chemistry calculations, allowing the assignment of the lowest-energy conformer with two rotamers depending on the orientation of the phenol hydroxyl (OH) group. The IR-UV hole burning spectrum exhibits the four expected vibrational modes in the 3 mum region, i.e., the phenol OH, Cbeta-OH, and two NH2(+) stretches. The striking difference is that, among these modes, only the free phenol OH mode is active through IRPD. The protonated amino group acts as a proton donor in the internal hydrogen bond and displays large frequency shifts upon isomerization expected during the multiphoton absorption process, leading to the so-called IRMPD transparency. More interestingly, while the Cbeta-OH is a proton acceptor group with moderate frequency shift for the different conformations, this mode is still inactive through IRPD.
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Noble, J. A., Broquier, M., Gregoire, G., Soorkia, S., Pino, G. A., Marceca, E., Dedonder-Lardeux, C., & Jouvet, C. (2018). Tautomerism and electronic spectroscopy of protonated 1- and 2-aminonaphthalene. Phys. Chem. Chem. Phys., 20, 6134–6145.
Résumé: Experimental and theoretical investigations of the excited states of protonated 1- and 2-aminonaphthalene are presented. The electronic spectra are obtained by laser induced photofragmentation of the ions captured in a cold ion trap. Using ab initio calculations, the electronic spectra can be assigned to different tautomers which have the proton on the amino group or on the naphthalene moiety. It is shown that the tautomer distribution can be varied by changing the electrospray source conditions, favoring either the most stable form in solution (amino protonation) or that in the gas phase (aromatic ring protonation). Calculations for larger amino-polyaromatics predict that these systems should behave as “proton sponges” i.e. have a proton affinity larger than 11 eV.
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Pérez-Mellor, A., Alata, I., Lepere, V., & Zehnacker, A. (2018). Chirality effects in the structures of jet-cooled bichromophoric dipeptides. Journal of Molecular Spectroscopy, 349, 71–84.
Résumé: Diastereomer cyclic dipeptides built on a diketopiperazine (DKP) ring and phenylalanine residues of either identical or opposite chirality have been studied in jet-cooled conditions by combining conformer-specific IR-UV laser spectroscopy. Comparison between the IR-UV double resonance experiments and anharmonic calculations shows the presence of only one conformer of cyclo Phe-Phe, with one aromatic ring folded on the dipeptide DKP ring and the other one extended. This allows weak NH…π and CH…π interactions to take place, which are slightly different in cyclo SPhe-SPhe and cyclo SPhe-RPhe. In both diastereomers, comparison between the S0 and S1 spectra of the all 12C species and that containing one 13C indicates that the electronic excitation is localized on one aromatic ring. This study has been extended to linear SPhe-SPhe and linear SPhe-RPhe, already studied by Abo-Riziq (2005).
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Peukert, S., Kijak, M., Ostapko, J., Sepiol, J., Le Bris, C., Zehnacker-Rentien, A., Gil, M., & Waluk, J. (2018). Supersonic jet spectroscopy of parent hemiporphycene: Structural assignment and vibrational analysis for S-0 and S-1 electronic states. Journal Of Chemical Physics, 149(13), 134307.
Résumé: Hemiporphycene (HPc), a constitutional isomer of porphyrin, is studied under supersonic expansion conditions by means of laser-induced fluorescence, visible-visible hole-burning experiments, single vibronic level fluorescence techniques, and quantum chemical calculations. Only one trans form of jet-cooled HPc is observed, in contrast to solution studies that evidence a mixture of two trans tautomeric forms separated in energy by similar to 1 kcal/mol. Reliable structural assignment is provided by simulating absorption and emission patterns at the density functional theory and time-dependent density functional theory levels of theory. The vibronic spectra are nicely reproduced for both electronic ground and lowest excited singlet states for the most stable trans form. In contrast to another porphyrin isomer, porphycene (Pc), no tunneling or photo-induced hydrogen transfer is detected. The lower symmetry of HPc compared with Pc and the concomitant non-equivalent positions of the inner-cavity nitrogen atoms result in a non-symmetric double minimum potential for tautomerization, larger energy barrier, and a longer tunneling distance, with the average intramolecular hydrogen bond length larger in HPc than in Pc. HPc readily forms hydrates that show red-shifted absorption relative to the bare molecule. Published by AIP Publishing.
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Pham, X. Q., Jonusauskaite, L., Depauw, A., Kumar, N., Lefevre, J. P., Perrier, A., Ha-Thi, M. - H., & Leray, I. (2018). New water-soluble fluorescent sensors based on calix[4]arene biscrown-6 for selective detection of cesium. Journal of Photochemistry and Photobiology A: Chemistry, 364, 355–362.
Résumé: Two new fluorescent chemosensors based on calix[4]arene bis(crown-6) bearing coumarin units have been synthesized for the detection of cesium ions in water. The photophysical and complexing properties of these sensors with cesium were investigated using absorption and fluorescence spectroscopies as well as DFT calculations. The coordination of Cs+ by the these ligands induces a better charge transfer between the donor and acceptor groups of the coumarin, resulting in a bathochromic shift in absorption spectra and an enhancement of emission spectra. Both the ligands display an excellent selectivity for Cs+ over other potentially interfering cations such as Na+, Li+, K+, Mg2+, Ca2+ and Sr2+ ions.
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Puglisi A., M. T., Kennedy E.T., Mosnier J.P., Bizau J.M., Cubaynes D., Sisourat N. and Carniato S. (2018). X-ray photochemistry of carbon hydride molecular ions. Physical Chemistry Chemical Physics, 20, 4415.
Résumé: Hydride molecular ions are key ingredients of the interstellar chemistry since they are precursors of more complex molecules. In regions located near a soft X-ray source these ions may resonantly absorb an X-ray photon which triggers a complex chain of reactions. In this work, we simulate ab initio the X-ray absorption spectrum, Auger decay processes and the subsequent fragmentation dynamics of two hydride molecular ions, namely CH2+ and CH3+. We show that these ions feature strong X-ray absorption resonances which relax through Auger decay within 7 fs. The doubly-charged ions thus formed mostly dissociate into smaller ionic carbon fragments: in the case of CH2+, the dominant products are either C+/H+/H or CH+/H+. For CH3+, the system breaks primary into CH2+ and H+, which provides a new route to form CH2+ near a X-ray source. Furthermore, our simulations provide the branching ratios of the final products formed after the X-ray absorption as well as their kinetic and internal energy distributions. Such data can be used in the chemistry models of the interstellar medium.
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Puthumpally-Joseph R., Mangaud E., Chevet V., Desouter-Lecomte M., Sugny D., & Atabek O. (2018). Basic mechanisms in the laser control of non-Markovian dynamics. Phys. Rev. A, 97(3), 033411.
Résumé: Referring to a Fano-type model qualitative analogy we develop a comprehensive basic mechanism for the laser control of the non-Markovian bath response and fully implement it in a realistic control scheme, in strongly coupled open quantum systems. Converged hierarchical equations of motion are worked out to numerically solve the master equation of a spin-boson Hamiltonian to reach the reduced electronic density matrix of a heterojunction in the presence of strong terahertz laser pulses. Robust and efficient control is achieved increasing by a factor of 2 the non-Markovianity measured by the time evolution of the volume of accessible states. The consequences of such fields on the central system populations and coherence are examined, putting the emphasis on the relation between the increase of non-Markovianity and the slowing down of decoherence processes.
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Ramos Chagas, G., Morán Cruz, G., Giraudon-Colas, G., Savina, F., Méallet-Renault, R., Amigoni, S., Guittard, F., & Darmanin, T. (2018). Anti-bacterial and fluorescent properties of hydrophobic electrodeposited non-fluorinated polypyrenes. Applied Surface Science, 452, 352–363.
Résumé: This work uses an innovative strategy to show a combination of highly hydrophobic films with fluorescence and anti-bacterial properties. Pyrene grafted with linear and branched alkyl chains of various length (from C4H9 to C12H25) were electropolymerized and their wetting behavior and surface morphology were first analyzed. The presence of microstructured spherical particles (1 µm) induces a high increase in the surface hydrophobicity (θw,max = 132°) even if the polymers are intrinsically hydrophilic (θY = 79–88°), while the surface oleophobicity decreases. The emission of the pyrene monomers and polymers is in the green region (λem = 479–515 nm) and showed to be related with the size and the architecture of the chain. The differences in the aggregations and interactions of the oligomers induce a blue-shift and a thinner spectral band for the branched pyrenes compared to the linear ones. A crescent batochromic and hypsochromic shift are observed for linear and branched chains, respectively, as the number of carbons increase. The polypyrenes also have a potential application to serve as coatings towards to prevention of biofilm formation. A reduction between 30–70% was observed for the bacterial adhesion and between 91–94% for the biofilm formation for S. aureus and P. aeruginosa strains. Here we showed for the first time that hydrophobic surfaces bearing hydrocarbon chains without fluorine atoms can be used towards to repel bacteria. Furthermore, the pyrene molecules lead to fluorescent and microstructured hydrophobic surfaces by a one-step electropolymerization process and the combination of these properties enhances the range of applications for these surfaces.
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Ramos, P., Mankarious, M., Pavanello, M., & Riedel, D. (2018). Probing Charge Transfer Dynamics in a Single Iron Tetraphenylporphyrin Dyad Adsorbed on an Insulating Surface. Nanoscale, 10(37), 17603–17616.
Résumé: Although the dynamics of charge transfer (CT) processes can be probed with ultimate lifetime resolution, the helplessness to control CT at the nanoscale constitutes one of the most important road-blocks to revealing some of its deep fundamental aspects. In this work, we present an investigation of CT dynamics in a single iron tetraphenylporphyrin (Fe-TPP) donor/acceptor dyad adsorbed on a CaF2/Si(100) insulating surface. The tip of a scanning tunneling microscope (STM) is used to create local ionic states in one fragment of the dyad. The CT process is monitored by imaging subsequent changes in the neighbor acceptor molecule and its efficiency is mapped revealing the influence of the initial excited state in the donor molecule. In validation of the experiments, simulations based on density functional theory show that holes have a higher donor acceptor CT rate compared to electrons and highlight a noticeable initial state dependence on the CT process. We leverage the unprecedented spatial resolution achieved in our experiments to show that the CT process in the dyad is governed via molecule-molecule coherent tunneling with negligible surface-mediated character.
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Rivera-Rivera, L. A., McElmurry, B. A., Scott, K. W., Springer, S. D., Lucchese, R. R., Bevan, J. W., Leonov, I. I., & Coudert, L. H. (2018). 6.2 μm spectrum and 6-dimensional morphed potentials of OC-H2O. Chemical Physics, 501(Supplement C), 35–45.
Résumé: Rovibrational transitions associated with tunneling states in the ν5 (water bending) vibration of the OC-H2O complex have been recorded using a supersonic jet mode-hop free quantum cascade laser spectrometer at 6.2 μm. Analysis of the resulting spectra is facilitated by incorporating fits of previously recorded microwave and submillimeter data accounting for Coriolis coupling. The theoretical basis of morphing a 5-D frozen monomers potential was initially developed and then extended to two 6-D morphed potentials. A combination of these spectroscopic results and previous rovibrational data for the ν5 vibration in OC-D2O are then used to generate a 6-D morphed potential surface for the intermolecular and the water bending vibrations. An alternative 6-D morphed potential of the intermolecular and the ν3 (CO stretching) vibrations was also generated. These determined morphed potentials then formed the basis for modeling the dynamics of the complex and prediction of accurate intermolecular rovibrational frequencies of the complex.
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Roncin, P., Debiossac, M., Oueslati, H., & Raouafi, F. (2018). Energy loss and inelastic diffraction of fast atoms at grazing incidence. NIM-B, 427, 100–107.
Résumé: The diffraction of fast atoms at grazing incidence on crystal surfaces (GIFAD) was first interpreted only in terms of elastic diffraction from a perfectly periodic rigid surface with atoms fixed at equilibrium positions. Recently, a new approach has been proposed, referred here as the quantum binary collision model (QBCM). The QBCM takes into account both the elastic and inelastic momentum transfers via the Lamb-Dicke probability. It suggests that the shape of the inelastic diffraction profiles are log-normal distributions with a variance proportional to the nuclear energy loss deposited on the surface. For keV Neon atoms impinging on a LiF(001) surface under an incidence angle θ, the predictions of the QBCM in its analytic version are compared with numerical trajectory simulations. Some of the assumptions such as the planar continuous form, the possibility to neglect the role of lithium atoms and the influence of temperature are investigated. A specific energy loss dependence ΔE θ ∝ 7 is identified in the quasi-elastic regime merging progressively to the classical onset ΔE θ ∝ 3. The ratio of these two predictions highlights the role of quantum effects in the energy loss.
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Sala, L., Szymańska, I. B., Dablemont, C., Lafosse, A., & Amiaud, L. (2018). Response under low-energy electron irradiation of a thin film of a potential copper precursor for focused electron beam induced deposition (FEBID). Beilstein J. Nanotechnol., 9, 57–65.
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Sekiguchi, T., Tamura, M., Oba, H., Carcarbal, P., Lozada-Garcia, R. R., Zehnacker-Rentien, A., Gregoire, G., Ishiuchi, S. - I., & Fujii, M. (2018). Molecular Recognition by a Short Partial Peptide of the Adrenergic Receptor: A Bottom-Up Approach. Angew Chem Int Ed Engl, 57, 5626–5629.
Résumé: Receptor-neurotransmitter molecular recognition is key for neurotransmission. Although crystal structures of the receptors are known, the mechanism for recognition is not clear. Reported here is the ultraviolet (UV) and infrared (IR) spectra of complexes between a partial peptide (SIVSF), mimicking the binding motif of a catechol ring in the adrenergic receptor, and various ligands. The UV spectra show that two isomers coexist in the complex of SIVSF with properly recognized ligands, such as protonated adrenaline (adrenalineH(+) ). From IR spectra, they are assigned to catechol- and amino-bound structures. The catechol-bound structure is not observed when the ligand is replaced by nonproper molecules, such as noradrenalineH(+) . The results suggest that SIVSF not only recognizes the catechol ring but can distinguish differences in the amine side chain. The method provides a new possibility for screening molecules as potential therapeutics for activating the receptor.
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Shafizadeh, N., Boyé-Péronne, S., Soorkia, S., Chen, S., de la Lande, A., Cunha de Miranda, B., Garcia, G. A., Nahon, L., Poisson, L., & Soep, B. (2018). The surprisingly high ligation energy of CO to Ruthenium porphyrins. Phys. Chem. Chem. Phys., 20, 11730–11739.
Résumé: A combined theoretical and experimental approach has been used to investigate the binding energy of a ruthenium metalloporphyrin ligated with CO, ruthenium tetraphenylporphyrin [RuII TPP], in the RuII oxidation degree. Measurements performed with VUV ionization using the DESIRS beamline at Synchrotron SOLEIL led to adiabatic ionization energies of [RuII TPP] and its complex with CO, [RuII TPP–CO], of 6.48
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Szczepaniak, U., Kolos R, Gronowski, M., Chevalier M, Guillemin, J. - C., & Crepin C. (2018). Synthesis and Electronic Phosphorescence of Dicyanooctatetrayne (NC10N) in Cryogenic Matrixes. J Phys Chem A, 122(25), 5580–5588.
Résumé: The rodlike 1,8-dicyano-octa-1,3,5,7-tetrayne (NC10N) molecule was synthesized with UV-assisted coupling of rare-gas matrix-isolated cyanobutadiyne (HC5N) molecules. Detection of NC10N molecule was possible due to its strong orange-red (origin at 618 nm) electronic luminescence. Excitation spectra of this emission (a (3)Sigmau(+)-X (1)Sigmag(+) phosphorescence) gave access to studying the fully allowed H (1)Sigmau(+)-X (1)Sigmag(+) UV system of NC10N. The identification of observed spectral features was assisted with quantum chemical computations. Certain regularities shaping the electronic spectroscopy of NC2 nN molecules have been discussed.
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Szczepaniak, U., Kołos, R., Gronowski, M., Guillemin, J. - C., & Crépin, C. (2018). Low Temperature Synthesis and Phosphorescence of Methylcyanotriacetylene. The Journal of Physical Chemistry A, 122(1), 89–99.
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Tchalala, M. R., Kara, A., Lachgar, A., Yagoubi, S., Foy, E., Vega, E., Nitsche, S., Chaudanson, D., Aufray, B., EL Firdoussi, L., Ali, M. A., & Oughaddou, H. (2018). Silicon nanoparticles synthesis from calcium disilicide by Redox assisted chemical exfoliation. Materials Today Communications, 16, 281–284.
Résumé: We report the preparation of single-crystal silicon nanoparticles with 15 to 22 nm diameter from calcium disilicide (CaSi2) by redox assisted chemical exfoliation using solution phase synthesis route. Silicon nanoparticles are found to be highly oriented with a predominant size of 18 nm. X-Ray diffraction, as well as transmission electron microscopy studies, confirm that the silicon nanoparticles are a diamond type and highly crystalline.
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Tchalala, R. M., Enriquez, H., Mayne, A. J., Kara, A., Dujardin, G., & Oughaddou, H. (2018). First steps of silicene growth on Ag(111). Journal of Physics: Conference Series, 1081, 012005.
Résumé: In this paper we report on the first steps of silicene growth on Ag(111) using scanning tunneling microscopy. We show that the topmost atomic layer is composed of both silicon and silver. The STM observations are consistent with an exchange process between the silicon and silver atoms preferentially taking place at the step edges of the Ag substrate. In addition, silicon stripes are observed as precursors of the formation of the silicene sheet.
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Tong, Y., Jiang, T., Qiu, S., Koshmak, K., Giglia, A., Kubsky, S., Bendounan, A., Chen, L., Pasquali, L., Esaulov, V. A., & Hamoudi, H. (2018). ZnO Functionalization: Metal–Dithiol Superstructures on ZnO(0001) by Self-Assembly. JOURNAL OF PHYSICAL CHEMISTRY C, 122(5), 2880–2889.
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Tran, T. - T., Ha-Thi, M. - H., Pino, T., Quaranta, A., Lefumeux, C., Leibl, W., & Aukauloo, A. (2018). Snapshots of Light Induced Accumulation of Two Charges on Methylviologen using a Sequential Nanosecond Pump–Pump Photoexcitation. The Journal of Physical Chemistry Letters, 9(5), 1086–1091.
Résumé: Methylviologen (MV2+) is perhaps the most used component as a reversible electron acceptor in photophysical studies. While MV2+ is most commonly implicated as a reversible one-electron mediator, its electrochemical properties clearly evidence two successive one-electron reduction processes. In this report, we have investigated on the light driven two-charge accumulation on MV2+ using a multicomponent system composed of the prototypical molecular photosensitizer [Ru(bpy)3]2+ and MV2+ in the presence of ascorbate as reversible electron donor. The sequential addition of two electrons on the methylviologen was tracked upon sequential excitation of the [Ru(bpy)3]2+ at optimized concentration of the electron acceptor. The charge accumulated state carries an energy of 0.9 eV above the ground state and has a lifetime of ca. 50 μs. We have reached a fairly good global yield of approximately 9% for the two-charge accumulation. This result clearly demonstrates the potential of this simple approach for applications in artificial photosynthesis.
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Uribe J. D., M. M., Fierro B., Cardoso-Gil R., Abril I., Garcia-Molina R., Valdés J. E., Esaulov V. A. (2018). Proton energy loss in multilayer graphene and carbon nanotubes. RADIATION EFFECTS AND DEFECTS IN SOLIDS, 173(1-2), 93–101.
Résumé: Results of a study of electronic energy loss of low keV protons interacting with multilayer graphene targets are presented. Proton energy loss shows an unexpectedly high value as compared with measurements in amorphous carbon and carbon nanotubes. Furthermore, we observe a classical linear behavior of the energy loss with the ion velocity but with an apparent velocity threshold around 0.1 a.u., which is not observed in other carbon allotropes. This suggests low dimensionality effects which can be due to the extraordinary graphene properties.
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Usabiaga, I., Camiruaga, A., Insausti, A., Carcabal, P., Cocinero, E. J., Leon, I., & Fernandez, J. A. (2018). Phenyl-beta-D-glucopyranoside and Phenyl-beta-D-galactopyranoside Dimers: Small Structural Differences but Very Different Interactions. Frontiers In Physics, 6, à venir.
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Zanuttini, D., Gatti, F., & Marquardt, R. (2018). CO quantum dynamics diffusion on Cu(1 0 0). Chemical Physics, 509, 3–12.
Résumé: We present a quantum mechanical study of the diffusion of CO molecules on the Cu(0 0 1) surface. We use the Strasbourg-Amsterdam-Postdam potential surface and a “non-tunnel”-variant hereof; to mimic an initial state that is localized in one adsorption well, a “local-potential-shift” concept is introduced; the Multi Configuration Time Dependent Hartree method to perform the calculations. Special emphasis is placed on the effect of the dimensionality of the models. Surprisingly, tunneling plays an important role typically 1 ps after the beginning of the dynamics; it dominates at around 1 ns and might, at least partly, explain the long diffusion rates measured experimentally for the system.
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Zhang, W., Enriquez, H., Tong, Y., Bendounan, A., Kara, A., Seitsonen, A. P., Mayne, A. J., Dujardin, G., & Oughaddou, H. (2018). Epitaxial Synthesis of Blue Phosphorene. SMALL, 14, 1804066.
Résumé: Phosphorene is a new 2D material composed of a single or few atomic layers of black phosphorus. Phosphorene has both an intrinsic tunable direct bandgap and high carrier mobility values, which make it suitable for a large variety of optical and electronic devices. However, the synthesis of single-layer phosphorene is a major challenge. The standard procedure to obtain phosphorene is by exfoliation. More recently, the epitaxial growth of single-layer phosphorene on Au(111) was investigated by molecular beam epitaxy and the obtained structure described as a blue phosphorene sheet. In the present study, large areas of high-quality monolayer phosphorene, with a bandgap value equal to at least 0.8 eV, are synthesized on Au(111). The experimental investigations, coupled with density functional theory calculations, give evidence of two distinct phases of blue phosphorene on Au(111), instead of one as previously reported, and their atomic structures are determined.
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Zhao, M., Almarzouqi, F., Duverger, E., Sonnet, P., Dujardin, G., & Mayne, A. J. (2018). Sub-molecular spectroscopy and temporary molecular charging of Ni-phthalocyanine on graphene with STM. Phys. Chem. Chem. Phys., 20(29), 19507–19514.
Résumé: In this study, the self-assembled molecular network and electronic properties of Ni-phthalocyanine (NiPc) molecules on monolayer graphene (MLG)/6H-SiC(0001) were studied by room temperature Scanning Tunnelling Microscopy (STM) and Density Functional Theory (DFT) calculations. In this study, a very weak electronic coupling between the graphene and the NiPc molecules is found. This is due to the very small charge transfer of only 0.035e- per molecule. The weak molecule-graphene interaction has two observable consequences: sub-molecular resolution was obtained in the STM spectroscopy at room-temperature with the molecules adsorbed directly on the graphene, and the occupied and unoccupied molecular resonance peaks were observed to shift their position in energy as a function of the tip-surface distance. This is due to the temporary local charging (either positive or negative) that is achieved by decreasing the surface voltage under the STM tip. This may have important consequences for future studies of the opto-electronic properties of such hybrid graphene-molecule systems.
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Zhao, Z. Q., Chen, J., Zhang, Z. J., Zhang, D. H., Wang, X. G., Carrington, T., & Gatti, F. (2018). Computing energy levels of CH4, CHD3, CH3D, and CH3F with a direct product basis and coordinates based on the methyl subsystem. JOURNAL OF CHEMICAL PHYSICS, 148(7), 074113.
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Actes de Conférences |
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Toullec, T., Mathieu, M. - C., Benoit, C., René Farcy, R., Tourasse, C., Boisserie-Lacroix, M., Fontaine-Aupart, M. - P., Delaloge, S., & Balleyguier, C. (2018). 25 gauge fibered-needle for label free fluorescence analysis of breast masses: a first in vivo study. In Proc.SPIE 10488, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications, (Vol. XVIII).
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