Peer-reviewed Publications |
Azzam, A. A. A., Yurchenko, S. N., Tennyson J., Martin-Drumel, M. A., & & Pirali, O. (2013). Terahertz spectroscopy of hydrogen sulfide. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 130, 341–351.
Résumé: Pure rotational transitions of hydrogen sulfide (H2S) in its ground and first excited vibrational states have been recorded at room temperature. The spectrum comprises an average of 1020 scans at 0.005 cm−1 resolution recorded in the region 45–360 cm−1 (1.4 to 10.5 THz) with a globar continuum source using a Fourier transform spectrometer located at the AILES beamline of the SOLEIL synchrotron. Over 2400 rotational lines have been detected belonging to ground vibrational state transitions of the four isotopologues H232S, H233S, H234S, and H236S observed in natural abundance. 65% of these lines are recorded and assigned for the first time, sampling levels as high as J=26 and Ka=17 for H232S. 320 pure rotational transitions of H232S in its first excited bending vibrational state are recorded and analysed for the first time and 86 transitions for H234S, where some of these transitions belong to new experimental energy levels. Rotational constants have been fitted for all the isotopologues in both vibrational states using a standard effective Hamiltonian approach. Comprehensive comparisons are made with previously available data as well as the data available in HITRAN, CDMS, and JPL databases. The 91 transitions assigned to H236S give the first proper characterization of its pure rotational spectrum.
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Beroff, K., Chabot, M., Martinet, G., Pino, T., Bouneau, S., Le Padellec, A., Feraud, G., Do Thi, N., Calvo, F., Bordas, C., & Lepine, F. (2013). Anion production in high-velocity cluster-atom collisions; the electron capture process revisited. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 46(1), 015201.
Résumé: Anion production cross sections in collisions between C-n(+), Cn carbon clusters (n <= 5) and helium atoms have been measured in high-velocity collisions (v = 2.25 and 2.6 au). This paper focuses on two of the three processes responsible for the C-n(-) production, namely double electron capture (DEC) onto C-n(+) cations and single electron capture onto neutral (SECN) C-n. They were experimentally distinguished from a gaseous thickness dependence study. Dissociative and non-dissociative cross sections were measured and, in the case of DEC, all dissociative branching ratios measured; for these small systems, the C-2(-) fragment was found magical. Data concerning electron capture in neutral-neutral collisions are extremely rare, especially at high velocity. Introduction of this measured process in the independent atom and electron (IAE) model allowed us to revisit and satisfactorily reproduce the so-far unexplained size evolution of single electron capture (SEC) cross sections in 2.6 au C-n(+)-He (n <= 10) collisions (Chabot et al 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2593-603). IAE calculations for DEC cross sections and their comparison with experiment suggest a loss of electron in anionic C-n(-) species after the collision, competing with fragmentation and depending on the size.
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Boudon, V., Asselin, P., Soulard, C., Goubet, M., Huet, A., Georges, R., Pirali, O., & & Roy, P. (2013). High-Resolution Spectroscopy and Analysis of the v2 + v3 Combination Band of SF6 in a Supersonic Jet Expansion. MOLECULAR PHYSICS, 111(14-15), 2154–2162.
Résumé: Sulphur hexafluoride is a very strong greenhouse gas whose concentration is increasing in the atmosphere. It is detected through infrared absorption spectroscopy in the strong ν3 fundamental region. Due to the existence of low-lying vibrational states of this molecule, however, many hot bands arise at room temperature and those are still not known. We present here a contribution to the elucidation of this hot band structure, by analysing the ν2 + ν3 combination band. We use a supersonic jet expansion high-resolution spectrum at a rotational temperature of ca. 25 K that was recorded thanks to the Jet-AILES setup at the Source Optimisée de Lumière d’Energie Intermédiaire du LURE (SOLEIL) Synchrotron. The simplified structure of this cold spectrum allowed us to assign 444 rovibrational lines and to fit effective Hamiltonian parameters, leading to a very satisfactory spectrum simulation. The parameters obtained in this way allow to calculate the spectrum of the ν3+ν2−ν2 hot band.
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Calvo, F., Falvo, C., & Parneix, P. (2013). A simple but accurate potential for the naphthalene-argon complex: Applications to collisional energy transfer and matrix isolated IR spectroscopy. JOURNAL OF CHEMICAL PHYSICS, 138(3), 034305.
Résumé: An explicit polarizable potential for the naphthalene-argon complex has been derived assuming only atomic contributions, aiming at large scale simulations of naphthalene under argon environment. The potential was parametrized from dedicated quantum chemical calculations at the CCSD(T) level, and satisfactorily reproduces available structural and energetic properties. Combining this potential with a tight-binding model for naphthalene, collisional energy transfer is studied by means of dedicated molecular dynamics simulations, nuclear quantum effects being accounted for in the path-integral framework. Except at low target temperature, nuclear quantum effects do not alter the average energies transferred by the collision or the collision duration. However, the distribution of energy transferred is much broader in the quantum case due to the significant zero-point energy and the higher density of states. Using an ab initio potential for the Ar-Ar interaction, the IR absorption spectrum of naphthalene solvated by argon clusters or an entire Ar matrix is computed via classical and centroid molecular dynamics. The classical spectra exhibit variations with growing argon environment that are absent from quantum spectra. This is interpreted by the greater fluxional character experienced by the argon atoms due to vibrational delocalization. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773469]
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Carpentier, Y., Pino, T., & Bréchignac, P. (2013). R2PI Spectroscopy of Aromatic Molecules Produced in an Ethylene-Rich Flame. JOURNAL OF PHYSICAL CHEMISTRY A, 117(39), 10092–10104.
Résumé: Laser spectroscopy, combined with mass spectrometry, was applied to study the spectra of aromatic molecules produced in a premixed ethylene-rich flat flame. These studies produce new gas-phase electronic spectra of polyaromatic compounds, which ultimately will guide the understanding of the chemical processes that lead to polycyclic aromatic hydrocarbon (PAH) growth or PAH formation locking. Resonant two-photon ionization (R2PI) spectra of all species detectable in a specific fuel-rich flame were recorded simultaneously during a single scan of the laser wavelength, within the 220–330 nm range. Comparison with spectra available in the literature allowed us to identify 16 aromatic species. In the PAH forming region of this flame, we found that the main PAHs are accompanied by a great diversity of other species, including in particular various side-chains on aromatic networks. We also show that this technique allows, at least in some cases, to distinguish between different isomers associated with the same mass peak, although the extracted PAHs are only cooled down to room temperature.
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Carré B., Poisson, L., Shafizadeh, N., & Soep, B. (2013). Stereodynamics of Chemical Reactions. Journal of Chemical Physics A, 117, 8093–8094.
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Chabot M., Beroff K., Gratier P., Jallat A., & Wakelam V. (2013). Reactions forming C(0;+) n=2;10, Cn=2;4H(0;+) and C3H(0;+) 2 in the gas phase: semi empirical branching ratios. The Astrophysical Journal, 771(90), 1–13.
Résumé: The aim of this paper is to provide a new set of branching ratios for interstellar and planetary chemical networks based on a semi empirical model. We applied, instead of zero order theory (i.e. only the most exoergic decaying channel is considered), a statistical microcanonical model based on the construction of
breakdown curves and using experimental high velocity collision branching ratios for their parametrization. We applied the model to ion-molecule, neutral-neutral, and ion-pair reactions implemented in the few popular databases for astrochemistry such as KIDA, OSU and UMIST. We studied the reactions of carbon and hydrocarbon species with electrons, He+, H+, CH+, CH, C, and C+ leading to intermediate
complexes of the type Cn=2;10, Cn=2;4H, C3H2, C+n =2;10, Cn=2;4H+, or C3H+2. Comparison of predictions with measurements supports the validity of the model. Huge deviations with respect to database values are often obtained. E ects of the new branching ratios in time dependant chemistry for dark clouds and for photodissociation region chemistry with conditions similar to those found in the Horsehead Nebula are discussed.
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Dartois E., Engrand C., Brunetto R., Duprat J., Pino T., Quirico E., Remusat L., Bardin N., Briani G., Mostefaoui S., Morinaud G., Crane B., S. N., Delauche L., Jamme F., Sandt Ch., & Dumas P. (2013). UltraCarbonaceous Antarctic micrometeorites, probing the Solar System beyond the nitrogen snow-line. ICARUS, 1(224), 243–252.
Résumé: The current Solar System architecture is a heritage of the protoplanetary disk that surrounded the young Sun, 4.56 Gy ago. Primitive extraterrestrial objects provide means to trace back the primordial composition and radial distribution of matter in this disk. Here, we present a combined micro-IR, Raman, chemical and isotopic study of two ultracarbonaceous micrometeorites recovered from Antarctica (UCAMMs). This study reveals particles containing an unusually high nitrogen- and deuterium-rich organic matter analogous to a polyaromatic hydrogenated carbon nitride, characterized by nitrogen concentration with bulk atomic N/C ratios of 0.05 and 0.12 (locally exceeding 0.15). We propose that such nitrogen-rich carbonaceous material can be formed by energetic irradiations of nitrogen-rich ices in very low temperature regions of the Solar System. Such conditions are encountered at the surface of small objects beyond the trans-neptunian region. UCAMMs provide unique insights on physico-chemical processes that occurred beyond the nitrogen snow-line, revealing organic material from the extreme outer regions of the Solar System that cannot be investigated by remote sensing methods.
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Dartois, E., Ding, J. J., de Barros, A. L. F., Boduch, P., Brunetto, R., Chabot, M., Domaracka, A., Godard, M., Lv, X. Y., Guaman, C. F. M., Pino, T., Rothard, H., da Silveira, E. F., & Thomas, J. C. (2013). Swift heavy ion irradiation of water ice from MeV to GeV energies. Approaching true cosmic ray compaction. ASTRONOMY & ASTROPHYSICS, 557, A97.
Résumé: Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles in space. One of the primary structural changes induced is the loss of porosity, and the mantles evolve toward a more compact amorphous state. Previously, ice compaction was monitored at low to moderate ion energies. The existence of a compaction threshold in stopping power has been suggested.
Aims. In this article we experimentally study the effect of heavy ion irradiation at energies closer to true cosmic rays. This minimises extrapolation and allows a regime where electronic interaction always dominates to be explored, providing the ice compaction cross section over a wide range of electronic stopping power.
Methods. High-energy ion irradiations provided by the GANIL accelerator, from the MeV up to the GeV range, are combined with in-situ infrared spectroscopy monitoring of ice mantles. We follow the IR spectral evolution of the ice as a function of increasing fluence (induced compaction of the initial microporous amorphous ice into a more compact amorphous phase). We use the number of OH dangling bonds of the water molecule, i.e. pending OH bonds not engaged in a hydrogen bond in the initially porous ice structure as a probe of the phase transition. These high-energy experiments are combined with lower energy experiments using light ions (H, He) from other facilities in Catania, Italy, and Washington, USA.
Results. We evaluated the cross section for the disappearance of OH dangling bonds as a function of electronic stopping power. A cross-section law in a large energy range that includes data from different ice deposition setups is established. The relevant phase structuring time scale for the ice network is compared to interstellar chemical time scales using an astrophysical model.
Conclusions. The presence of a threshold in compaction at low stopping power suggested in some previous works seems not to be confirmed for the high-energy cosmic rays encountered in interstellar space. Ice mantle porosity or pending bonds monitored by the OH dangling bonds is removed efficiently by cosmic rays. As a consequence, this considerably reduces the specific surface area available for surface chemical reactions.
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Debnath, A., Falvo, C., & Meier, C. (2013). State-Selective Excitation of the CO Stretch in Carboxyhemoglobin by Mid-IR Laser Pulse Shaping: A Theoretical Investigation. JOURNAL OF PHYSICAL CHEMISTRY A, 117, 12884−12888.
Résumé: We present simulations of the excitation of specific vibrational levels of
the CO stretch in carboxyhemoglobin by shaped mid-IR laser pulses. The pulses are
calculated using local control theory, adapted to account for the protein fluctuations, which are included using a microscopic model developed previously. We show that efficient selective vibrational state preparation can be obtained, despite the presence of the fluctuations and orientational averaging, and can be monitored using transient absorption spectra. The mid-IR pulses are found to be in a realistic intensity regime and might soon be available by IR pulse shaping. This opens the way to a direct monitoring of vibrational relaxation from individually prepared, high-lying vibrational states of complex systems.
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Falvo, C., Friha, H., Pino, T., Dhaouadi, Z., Parneix, P., Calvo, F., & and Brechignac, P. (2013). Effects of hydrogen dissociation on the infrared emission spectra of naphthalene: theoretical modeling. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10241–10250.
Résumé: The IR emission spectroscopy of naphthalene and its singly- and doubly-dehydrogenated radicals has been modeled using kinetic Monte Carlo simulations, taking into account the various relaxation pathways of radiative emission and hydrogen loss. Our modeling relies on quantum chemistry ingredients that were obtained from dedicated calculations based on density functional theory, including explicitly anharmonicity contributions. Our results show that the fragmentation products significantly contribute to the overall IR emission spectrum, especially to the intensity ratios between bands. Owing to the likely presence of polycyclic aromatic hydrocarbons in the interstellar medium, these findings are particularly relevant in the astrophysical context.
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Falvo, C., Debnath, A., and Meier, C. (2013). Vibrational ladder climbing in carboxy-hemoglobin: Effects of the protein environment. JOURNAL OF CHEMICAL PHYSICS, 138, 145101.
Résumé: We present simulations on vibrational ladder climbing in carboxy-hemoglobin. Motivated by recent experiments, we study the influence of different realistic pump probe parameters. To allow for a direct comparison with experimental results, transient absorption spectra obtained by a weak probe pulse following the strong, shaped pump pulse are calculated. The influence of the protein fluctuations is taken into account using a recently developed microscopic model. This model consists of a quantum Hamiltonian describing the CO vibration in carboxy-hemoglobin, together with a fluctuating potential, which is obtained by electronic structure calculation based on a large number of protein configurations. Using realistic pulse parameters, vibrational excitations to very high-lying states are possible, in qualitative agreement with experimental observations.
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Friha, H., Féraud, G., Troy, T., Falvo, C., Parneix, P., Bréchignac, P., Dhaouadi, Z., Schmidt, T. W., & Pino, T. (2013). Visible Photodissociation Spectra of the 1- and 2-Methylnaphthalene Cations: Laser Spectroscopy and Theoretical Simulations. JOURNAL OF PHYSICAL CHEMISTRY A, 117, 13664–13672.
Résumé: The electronic absorption spectra of the two methyl derivatives of the naphthalene cation were measured using an argon tagging technique. In both cases, a band system was observed in the visible range and assigned to the D2 ← D0 electronic transition. The 1-methylnaphthalene+ absorption bands revealed a red shift of 808 cm–1, relative to those of the naphthalene cation (14 906 cm–1), whereas for 2-methylnaphthalene+ a blue shift of 226 cm–1 appeared. A short vibrational progression, similar to the naphthalene cation, was also observed for both isomers and found to involve similar aromatic ring skeleton vibrations. Moreover, insights into the internal rotation motion of the methyl group were inferred, although the spectral resolution was not sufficient to fully resolve the substructure. These measurements were supported by detailed quantum chemical calculations. They allowed exploration of the potential energy curves along this internal coordinate, along with a complete simulation of the harmonic Franck–Condon factors using the cumulant Gaussian fluctuations formalism extended to include the internal rotation.
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Gans, B., Peng, Z., Carrasco, N., Gauyacq, D., Lebonnois, S., & Pernot, P. (2013). Impact of a new wavelength-dependent representation of methane photolysis branching ratios on the modeling of Titan's atmospheric photochemistry. ICARUS, 223(1), 330–343.
Résumé: A new wavelength-dependent model for CH4 photolysis branching ratios is proposed, based on the values measured recently by Gans et al. (Gans, B. et al. [2011]. Phys. Chem. Chem. Phys. 13,8140-8152). We quantify the impact of this representation on the predictions of a photochemical model of Titan's atmosphere, on their precision, and compare to earlier representations. Although the observed effects on the mole fraction of the species are small (never larger than 50%), it is possible to draw some recommendations for further studies: (i) the Ly-alpha branching ratios of Wang et al. (Wang, J.H. et al. [2000]. J. Chem. Phys. 113, 4146-4152) used in recent models overestimate the CH2:CH3 ratio, a factor to which a lot of species are sensitive; (ii) the description of out-of-Ly-alpha branching ratios by the “100% CH3” scenario has to be avoided, as it can bias significantly the mole fractions of some important species (C3H8); and (iii) complementary experimental data in the 130-140 nm range would be useful to constrain the models in the Ly-alpha deprived 500-700 km altitude range. (C) 2012 Elsevier Inc. All rights reserved.
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Gruet S., Morvan, A., Pirali O., Chamaillé T., Bouisset E., & Vervloet M. (2013). Fourier transform far-infrared spectroscopy of HN2+ on the AILES beamline of synchrotron SOLEIL. Canadian Journal of Physics, 91(11), 937–940.
Résumé: Nous présentons le spectre de rotation pure de HN2+ mesuré par spectroscopie d'absorption à transformée de Fourier (FT) dans le domaine spectral 20–40 cm–1. Les cations sont produits dans une cellule à décharge à cathode creuse refroidie a l'azote liquide, qui a été développée sur la ligne AILES du synchrotron SOLEIL. Le montage a été optimisé par la mesure des spectres de rotation–vibration de H3+ (bande ν2 centrée autour de 2521 cm–1), de HN2+ (bande ν1 centrée autour de 3234 cm–1), et de HCO+ (bande ν1 centrée autour de 3089 cm–1). Plusieurs raies de rotation–vibration ont été attribuées pour chaque ion et cinq transitions de rotation pure ont été identifiées pour HN2+. Ces résultats démontrent la faisabilité d'enregistrer des spectres de cations dans l'infrarouge lointain en utilisant une spectroscopie FT à large bande comme alternative aux techniques basées sur des lasers à fréquence ajustable.
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Ha-Thi M.H, Shafizadeh N., Poisson, L., & Soep, B. (2013). An Efficient Indirect Mechanism for the Ultrafast Intersystem Crossing in Copper Porphyrins. Journal of Chemical Physics A, 117, 8111–8118.
Résumé: The ultrafast dynamics of copper tetraphenylporphyrin (CuTPP), copper octaethylporphyrin (CuOEP) and of the free base tetraphenylporphyrin (H2TPP), excited in the S2. state have been investigated in the gas phase by femtosecond pump/probe experiments. The porphyrins were excited in the Soret band at 400 nm. Strikingly, the S2.-S1. internal conversion in H2TPP is very rapid (110 fs), as compared to that of ZnTPP (600 fs), previously observed. In turn, CuTPP and CuOEP, excited in S2., follow a different relaxation pathway from that of other open-shell metalloporphyrins. These two molecules exhibit a four-step decay ending on a slow evolution in the nanosecond range 2S2.→ 2CT→ 2T→ 2Ground State. This latter evolution is linked to the formation of the 2T, Tripdoublet state in CuTPP, observed in the condensed phase. It is shown that an intermediate charge transfer state plays a crucial role in linking the porphyrin centered 1ππ* and 3ππ* configurations. A simple model is presented that allows a rapid evolution between these two configurations, via coupling with the free d electron on the copper, getting around the spin orbit coupling in the porphyrin π.
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Hartmann, J. - M., Boulet, C., Vieillard, T., Chaussard, F., Billard, F., Faucher, O., & Lavorel, B. (2013). Dissipation of alignment in CO2 gas: A comparison between ab initio predictions and experiments. JOURNAL OF CHEMICAL PHYSICS, 139(2), 024306.
Résumé: We present comparisons between measurements and ab initio calculations of the dissipation of the nonadiabatic laser-induced alignment in pure CO2 and CO2-He gas mixtures. The experiments were made for pressures between 2 and 20 bars at 295 K by using short non-resonant linearly polarized laser pulses for alignment and probe. The calculations are carried, free of any adjusted parameter, using refined intermolecular potentials and a requantized Classical Molecular Dynamics Simulations approach presented previously but not yet confronted to experiments. The results demonstrate that the model accurately reproduces the decays with time of both the transient revivals and “permanent” component of the alignment. The significant differences observed between the behaviors resulting from CO2-CO2 and CO2-He collisions are also well predicted by the model. (C) 2013 AIP Publishing LLC.
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Hartmann, J. - M., Sironneau, V., Boulet, C., Svensson, T., Hodges, J. T., & Xu, C. T. (2013). Collisional broadening and spectral shapes of absorption lines of free and nanopore-confined O-2 gas. PHYSICAL REVIEW A, 87(3), 032510.
Résumé: This paper presents fully ab initio calculations of the broadenings and spectral shapes of O-2 infrared absorption lines in a free gas and when confined in nanoporous media. These calculations are performed, without use of any adjusted parameter, using a recently proposed approach [Phys. Rev. A 87, 013403 (2013)] that is based on requantized classical molecular-dynamics simulations. This involves studying the time evolutions of the translational and rotational motions of large numbers of molecules taking molecule-molecule and molecule-surface collisions into account through realistic interaction potentials. These simulations enable predictions of dipole autocorrelation functions whose Fourier-Laplace transforms yield the associated spectra. Comparisons are then made with broadening coefficients and line shapes provided by new and previous experiments. The good agreement between calculated and measured results confirms the veracity of the proposed model for a free gas and shows that the effects of confinement, which induce significant modifications to the line shapes, are correctly predicted. The need for improved characterization of the shape and size of pores in random nanoporous media is highlighted. DOI: 10.1103/PhysRevA.87.032510
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Coherent Raman spectro-imaging with laser frequency combs. Nature, 502(7471), 355–8.
Résumé: Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques.
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Ma, Q., Boulet, C., & Tipping, R. H. (2013). Refinement of the Robert-Bonamy formalism: Considering effects from the line coupling. JOURNAL OF CHEMICAL PHYSICS, 139(3), 034305.
Résumé: Since it was developed in 1979, the Robert-Bonamy (RB) formalism has been widely used in calculating pressure broadened half-widths and induced shifts for many molecular systems. However, this formalism contains several approximations whose applicability has not been thoroughly justified. One of them is that lines of interest are well isolated. When these authors developed the formalism, they have relied on this assumption twice. First, in calculating the spectral density F(omega), they have only considered the diagonal matrix elements of the relaxation operator. Due to this simplification, effects from the line mixing are ignored. Second, when they applied the linked cluster theorem to remove the cutoff, they have assumed the matrix elements of the operator exp(-iS(1) – S-2) can be replaced by the exponential of the matrix elements of -iS(1) – S-2. With this replacement, effects from the line coupling are also ignored. Although both these two simplifications relied on the same approximation, their validity criteria are completely different and the latter is more stringent than the former. As a result, in many cases where the line mixing becomes negligible, significant effects from the line coupling have been completely missed. In the present study, we have developed a new method to evaluate the matrix elements of exp(-iS(1) – S-2) and have refined the RB formalism such that line coupling can be taken into account. Our numerical calculations of the half-widths for Raman Q lines of the N-2-N-2 pair have demonstrated that effects from the line coupling are important. In comparison with values derived from the RB formalism, new calculated values for these lines are significantly reduced. A recent study has shown that in comparison with the measurements and the most accurate close coupling calculations, the RB formalism overestimates the half-widths by a large amount. As a result, the refinement of the RB formalism goes in the right direction and these new calculated half-widths become closer to the “true” values. (C) 2013 AIP Publishing LLC.
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Makarov, D. S., Tretyakov, M. Y., & Boulet, C. (2013). Line mixing in the 60-GHz atmospheric oxygen band: Comparison of the MPM and ECS model. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 124, 1–10.
Résumé: Precise profiles of the 60-GHz molecular oxygen band recorded earlier in a wide temperature range by means of a resonator spectrometer at atmospheric pressure were treated. High signal-to-noise ratio allows careful study of the band shape taking into consideration the mixing effect. Comparative analysis of the band profile calculated by an extended MPM (Millimeter-wave Propagation Model) and by the ECS (Energy Corrected Sudden) approximation model is presented. Some limitations of the MPM approach are discussed on the basis of the comparison of the two models. Interbranch coupling is shown to make a noticeable contribution to absorption which means that it should be taken into account as it is expected to improve band profile modeling accuracy. (c) 2013 Elsevier Ltd. All rights reserved.
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Martin-Drumel, M. A., Pirali, O., Loquais, Y., Falvo, C., & Brechignac, P. (2013). Lowest energy vibrational modes of some naphthalene derivatives: Azulene, quinoline, isoquinoline – Experiment and theory. CHEMICAL PHYSICS LETTERS, 557, 53–58.
Résumé: Far infrared (FIR) gas phase absorption spectra of azulene, quinoline and isoquinoline have been recorded using a Fourier transform Bruker IFS125 interferometer at medium resolution (0.5 cm(-1)). Assignments of these weak vibrational bands were performed using density-functional theory calculations carried out at the harmonic and anharmonic levels. Agreement between observed and calculated band positions is better than 5% for azulene and 1% for quinoline and isoquinoline. The relative band intensities are also correctly predicted. Molecular structure dependence of the FIR spectra is discussed based on the comparative study of three selected FIR modes. (C) 2012 Elsevier B.V. All rights reserved.
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Orthous-Daunay, F. R., Quirico, E., Beck, P., Brissaud, O., Dartois, E., Pino, T., & Schmitt, B. (2013). Mid-infrared study of the molecular structure variability of insoluble organic matter from primitive chondrites. ICARUS, 223(1), 534–543.
Résumé: Insoluble Organic Matter (IOM) found in primitive meteorites was formed in the Early Solar System and subsequently processed on the parent asteroids. The location, temporal sequence and processes of formation of this IOM are still a matter of debate. In particular, there is no consensus on the actual effect of post-accretional aqueous alteration processes on the chemical composition and structure of IOM. In the most primitive chondrites (types I and 2), these alterations have so far been either neglected or generically assigned to oxidation processes induced by fluid circulation. A series of IOM samples extracted from 14 chondrites with extensively documented post-accretional histories have been studied by infrared spectroscopy. Aqueous alteration shows no detectable effect on the chemical composition and structure of IOM within or across chondrite classes. Indeed, the most effective post-accretional process appears to be a high-temperature short-duration heating event and concerns essentially type 2 chondrites. In any case, post-accretional processes cannot account for all the chemical and structural variations of IOM. Chondrites from the CI, CR and CM classes accreted IOM precursors with moderately variable compositions, suggesting a chemical heterogeneity of the protosolar disk. The 3.4 μm band, and possibly its overtones and combinations in the near-infrared range, appear to be tracer(s) of the chemical class and possibly of surface heating processes triggered by impacts. (C) 2013 Elsevier Inc. All rights reserved.
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Parneix P., Basire M., & Calvo F. (2013). Accurate Modeling of Infrared Multiple Photon Dissociation Spectra: The Dynamical Role of Anharmonicities. JOURNAL OF PHYSICAL CHEMISTRY A, 117(19), 3954–3959.
Résumé: The dynamical response of a molecular system to a macropulse typically produced by a free-electron laser is theoretically modeled over experimentally long times, within a realistic kinetic Monte Carlo framework that incorporates absorption, stimulated emission, spontaneous emission, and dissociation events. The simulation relies on an anharmonic potential energy surface obtained from quantum chemistry calculations. Application to cationic naphthalene yields a better agreement with measurements than the anharmonic linear absorption spectrum, thus emphasizing the importance of specific dynamical effects on the spectral properties.
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Pirali O., Goubet M., Huet T.R., Georges R., Soulard P., Asselin P., Courbe J., Roy P., & & Vervloet M. (2013). The far infrared spectrum of naphthalene characterized by high resolution synchrotron FTIR spectroscopy and anharmonic DFT calculations. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15, 10141–10150.
Résumé: Using synchrotron radiation, we performed the rotationally resolved Fourier transform infrared absorption spectroscopy of three bands of naphthalene C10H8, namely ν46-0 (centered at 782 cm−1, 12.7 μm), ν47-0 (centered at 474 cm−1, 21 μm), and ν48-0 (centered at 167 cm−1, 60 μm). The intense CH bending out of plane ν46-0 band was recorded under supersonic jet-cooled conditions using a molecular beam (the Jet-AILES apparatus) and the low frequency ν47-0 and ν48-0 bands were measured at room temperature in a long absorption path cell. The simultaneous rotational analysis of these bands permitted us to refine the ground state (GS) and ν46 rotational spectroscopic constants and to provide the first sets of constants for the ν47 and ν48 modes. The experimental rotational constants were then used as reference data to calibrate theoretical models in order to provide new insights into the accuracy of anharmonic calculations. The B97-1 functional associated with the cc-pVTZ and ANO-RCC basis sets gave a consistent set of results, for rotational constants and fundamental frequencies. The data presented here pave the way for the search of naphthalene through its far-infrared spectrum in different objects of the interstellar medium.
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Tudorie, M., Kleiner, I., Jahn, M., Grabow, J. U., Goubet, M., & Pirali, O. (2013). Coupled Large Amplitude Motions: A Case Study of the Dimethylbenzaldehyde Isomers. Journal of Physical Chemistry A, 117(50), 13636–13647.
Résumé: The microwave spectra of the 3,4- (syn and anti), 2,5- (syn), and 3,5-dimethylbenzaldehyde (DMBA) molecules have been recorded for the first time in the 2–26.5 GHz frequency range, using the high resolution COBRA-FTMW spectrometer in Hannover. The experimental assignments and fits are supplemented by ab initio quantum chemical calculations of the conformational energy landscape and dipole moment components. The analysis of the spectra of the four observed isomers, including spectroscopic constants and large amplitude motion parameters, are presented in this paper. The DMBA isomers belong to a series of similar molecules obtained formally by adding one or more methyl group(s) at the aromatic ring. These molecules serve as prototype systems for the development of the theoretical model of asymmetric top molecules having Cs symmetry while containing in addition two nonequivalent methyl tops (C3v), exhibiting different barrier heights and coupling terms. Thus, the DMBA isomers represent good species for testing the recently written two-top internal rotors BELGI program.
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Vander Auwera, J., Ngo, N. H., El Hamzaoui, H., Capoen, B., Bouazaoui, M., Ausset, P., & Boulet, C. and H., J.-M. (2013). Infrared absorption by molecular gases as a probe of nanoporous silica xerogel and molecule-surface collisions: Low-pressure results. PHYSICAL REVIEW A, 88(042506), 042506.
Résumé: Transmission spectra of gases confined (but not adsorbed) within the pores of a 1.4-cm-thick silica xerogel sample have been recorded between 2.5 and 5 μm using a high-resolution Fourier transform spectrometer. This was done for pure CO, CO2, N2O, H2O, and CH4 at room temperature and pressures of a few hectopascals. Least-squares fits of measured absorption lines provide the optical-path lengths within the confined (LC) and free (LF) gas inside the absorption cell and the half width at half maximum ΓC of the lines of the confined gases. The values of LC and LF retrieved using numerous transitions of all studied species are very consistent. Furthermore, LC is in satisfactory agreement with values obtained from independent measurements, thus showing that reliable information on the open porosity volume can be retrieved from an optical experiment. The values of ΓC, here resulting from collisions of the molecules with the inner surfaces of the xerogel pores, are practically independent of the line for each gas and inversely proportional to the square root of the probed-molecule molar mass. This is a strong indication that, for the studied transitions, a single collision of a molecule with a pore surface is sufficient to change its rotational state. A previously proposed simple model, used for the prediction of the line shape, leads to satisfactory agreement with the observations. It also enables a determination of the average pore size, bringing information complementary to that obtained from nitrogen adsorption porosimetry.
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Vieillard, T., Chaussard, F., Billard, F., Sugny, D., Faucher, O., Ivanov, S., Hartmann, J. - M., Boulet, C., & Lavorel, B. (2013). Field-free molecular alignment for probing collisional relaxation dynamics. PHYSICAL REVIEW A, 87(2), 023409.
Résumé: We report the experimental study of field-free molecular alignment in CO2 gas mixtures induced by intense femtosecond laser pulses in the presence of collisional processes. We demonstrate that the alignment signals exhibit specific features due to nontrivial collisional propensity rules that tend to preserve the orientation of the rotational angular momentum of the molecules. The analysis is performed with a quantum approach based on the modeling of rotational J- and M-dependent state-to-state transfer rates. The present work paves the way for strong-field spectroscopy of collisional dynamics. DOI: 10.1103/PhysRevA.87.023409
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Wang, C. Y., Herr, T., Del'Haye, P., Schliesser, A., Hofer, J., Holzwarth, R., Haensch, T. W., Picque, N., & Kippenberg, T. J. (2013). Mid-infrared optical frequency combs at 2.5 μm based on crystalline microresonators. NATURE COMMUNICATIONS, 4, 1345.
Résumé: The mid-infrared spectral range (lambda similar to 2-20 μm) is of particular importance as many molecules exhibit strong vibrational fingerprints in this region. Optical frequency combs-broadband optical sources consisting of equally spaced and mutually coherent sharp lines-are creating new opportunities for advanced spectroscopy. Here we demonstrate a novel approach to create mid-infrared optical frequency combs via four-wave mixing in a continuous-wave pumped ultra-high Q crystalline microresonator made of magnesium fluoride. Careful choice of the resonator material and design made it possible to generate a broadband, low-phase noise Kerr comb at lambda = 2.5 μm spanning 200 nm (approximate to 10 THz) with a line spacing of 100 GHz. With its distinguishing features of compactness, efficient conversion, large mode spacing and high power per comb line, this novel frequency comb source holds promise for new approaches to molecular spectroscopy and is suitable to be extended further into the mid-infrared.
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Actes de Conférences |
Carpentier, Y., Feraud, G., Dartois, E., Brunetto, R., Charon, E., Cao, A. T., d'Hendecourt, L., Brechignac, P., Rouzaud, J. N., & Pino, T. (2013). NANOSTRUCTURATION OF POLYAROMATIC ANALOGUES OF THE CARBONACEOUS DUST. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 399–404).
Résumé: Carbonaceous cosmic dust is mainly observed through infrared spectroscopy either in absorption or in emission. Laboratory soot analogues of this interstellar or circumstellar dust were produced in fuel-rich, low-pressure, premixed and flat, flames. The particles were investigated by infrared absorption spectroscopy in the 2-15 μm spectral region. The details of the spectral features shed some light on the structure of the material and enable the study of its life cycle. In particular, the 8 μm band position is tentatively attributed to defects at the edge or in the polyaromatic units of the materials, revealing these structural changes in astrophysical dust.
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Feraud, G., Carpentier, Y., Pino, T., Longval, Y., Dartois, E., Chamaille, T., Vasquez, R., Vincent, J., Parneix, P., Falvo, C., & Brechignac, P. (2013). INFRARED EMISSION FROM PHOTO-EXCITED GASEOUS BENZENE: DETECTION WITH A NEW HOME-MADE SPECTROMETER. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 379–384).
Résumé: The infrared fluorescence decay and the dispersed emission spectrum are presented for gaseous benzene following 193 nm laser excitation. They were measured with FIREFLY (Fluorescence in the Infra Red from Excited FLYing molecules), a new home-made spectrometer. Redshift and redtail in the CH stretch emission spectra (3.3 μm region) demonstrate that anharmonicity plays a key role when dealing with high internal energies, as it is the case in the interstellar medium.
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Friha, H., Feraud, G., Pino, T., Parneix, P., Dhaouadi, Z., & Brechignac, P. (2013). ELECTRONIC SPECTRA OF CATIONIC PAH AND PAH CLUSTERS. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 373–378).
Résumé: An experiment designed for measuring the electronic spectra of PAH cations and PAH cluster cations has been set up, which is briefly described. The photodissociation spectra, reflecting the absorption spectra, of 2-methyl-naphthalene dimer cation have been recorded in the spectral ranges corresponding to the transitions from the ground state to both the excited charge resonance state and the first allowed local electronic excitation state.
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Godard, M., Feraud, G., Chabot, M., Carpentier, Y., Pino, T., Brunetto, R., Duprat, J., Engrand, C., Brechignac, P., d'Hendecourt, L., & Dartois, E. (2013). EFFECTS OF COSMIC RAYS ON HYDROCARBON INTERSTELLAR DUST. In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 395–398).
Résumé: Hydrogenated amorphous carbons, an important component of the interstellar carbonaceous dust, possess infrared spectral signatures (at 3.4, 6.9 and 7.3 μm) that are ubiquitous in the diffuse interstellar medium of galaxies, but not observed in dense clouds. To better understand the role played by cosmic rays in the disappearance of these absorption bands, irradiation experiments of hydrocarbon dust analogues have been performed with different swift ions. The results obtained through the in situ infrared monitoring of the samples during the irradiations allow to infer the dehydrogenation effect of the cosmic ray distribution on the interstellar hydrogenated amorphous carbons. The importance of this interstellar dust destruction by cosmic rays is discussed in comparison to other energetic processes in different interstellar environments.
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Holzner, S., Ideguchi, T., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Dual-Comb Coherent Raman Spectro-Imaging. In 2013 Conference On Lasers And Electro-Optics Pacific Rim (Cleo-Pr).
Résumé: Ultra-rapid coherent Stokes and anti-Stokes Raman spectroscopy with two laser frequency combs is demonstrated. Spectra and hyperspectral images are measured over a span of 1200 cm(-1) at 4 cm(-1) resolution within 15 microseconds.
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Holzner, S., Ideguchi, T., Guelachvili, G., Hansch, T. W., & Picque, N. (2013). Simultaneous Coherent Stokes and Anti-Stokes Raman Spectroscopy with Two Laser Frequency Combs. In 2013 Conference On Lasers And Electro-Optics (Cleo).
Résumé: We present a new technique of non-linear dual-comb spectroscopy for the measurement of coherent Stokes and anti-Stokes Raman spectra of fundamental vibrational transitions. Ultra-rapid acquisition times, high-resolution, broad-spectral-span are the main characteristics of our experiments.
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Coherent anti-Stokes Raman dual-comb spectro-microscopy. In 2013 Conference On Lasers And Electro-Optics (Cleo).
Résumé: Ultra-rapid coherent anti-Stokes Raman spectroscopy with two laser frequency combs is demonstrated. Hyperspectral images are acquired over a spectral bandwidth of 1200 cm(-1) with a resolution of 10 cm(-1) at a rate of 50 pixels/s.
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Ideguchi, T., Holzner, S., Bernhardt, B., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Ultra-rapid coherent anti-Stokes Raman dual-comb spectroscopy and microscopy. In 2013 Conference On And International Quantum Electronics Conference Lasers And Electro-Optics Europe (Cleo Europe/Iqec).
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Ideguchi, T., Poisson, A., Guelachvili, G., Picque, N., & Hansch, T. W. (2013). Adaptive Dual-Comb Spectroscopy with Free-Running Lasers. In 2013 Conference On Lasers And Electro-Optics Pacific Rim (Cleo-Pr).
Résumé: A new concept of real-time dual-comb spectroscopy that only uses free-running femtosecond mode-locked lasers provides high quality Fourier spectra with resolved comb lines over 12 THz spectral span without a posteriori data processing.
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Martin-Drumel, M. A., Pirali, O., Eliet, S., & Cuisset, A. (2013). HIGH RESOLUTION FAR INFRARED LABORATORY SPECTROSCOPY OF TRANSIENT SPECIES: APPLICATION TO THE SO RADICAL (X-3 Sigma). In ECLA: EUROPEAN CONFERENCE ON LABORATORY ASTROPHYSICS (Vol. 58, pp. 279–282).
Résumé: Both emission and absorption techniques have been developed at the AILES beamline of SOLEIL synchrotron to record far infrared (FIR) spectra of transient species. To illustrate the possibilities offered by our absorption set-up, we report in this paper new rotational transitions of the SO radical falling in the spectral range covered by the HIFI spectrometer onboard Herschel.
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Pino T., C. Y.,. Féraud G, Bréchignac Ph., Brunetto R., d'Hendecourt L., Dartois E., & Rouzaud J.-N. (2013). LABORATORY ANALOGUES OF THE CARBONACEOUS DUST: SYNTHESIS OF SOOT-LIKE MATERIALS AND THEIR PROPERTIES. In Highlights of Astronomy, XXVIIIth IAU General Assembly.
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Chapitres de Livres |
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Falvo, C., Sanda, F., & Mukamel, S. (2013). Quasi-Particle Approach to 2D IR Spectra of Vibrational Excitons in Biomolecules. In CRC Press (Ed.), Ultrafast Infrared Vibrational Spectroscopy. M. D. Fayer.
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