Peer-reviewed Publications |
Amyay B., Louviot M., Pirali O., Georges R., Vander Auwera J., & Boudon V. (2016). Global analysis of the high temperature infrared emission spectrum of 12CH4 in the dyad (ν2/ν4) region. JOURNAL OF CHEMICAL PHYSICS, 144(2), 024312.
Résumé: We report new assignments of vibration-rotation line positions of methane (12CH4) in the so-called dyad (ν2/ν4) region (1100–1500 cm−1), and the resulting update of the vibration-rotation effective model of methane, previously reported by Nikitin et al. [Phys. Chem. Chem. Phys. 15, 10071 (2013)], up to and including the tetradecad. High resolution (0.01 cm−1) emission spectra of methane have been recorded up to about 1400 K using the high-enthalpy source developed at Institut de Physique de Rennes associated with the Fourier transform spectrometer of the SOLEIL synchrotron facility (AILES beamline). Analysis of these spectra allowed extending rotational assignments in the well-known cold band (dyad-ground state (GS)) and related hot bands in the pentad–dyad system (3000 cm−1) up to Jmax = 30 and 29, respectively. In addition, 8512 new transitions belonging to the octad–pentad (up to J = 28) and tetradecad-octad (up to J = 21) hot band systems were successfully identified. As a result, the MeCaSDa database of methane was significantly improved. The line positions assigned in this work, together with the information available in the literature, were fitted using 1096 effective parameters with a dimensionless standard deviation σ = 2.09. The root mean square deviations dRMS are 3.60 × 10−3 cm−1 for dyad-GS cold band, 4.47 ×10−3 cm−1 for the pentad–dyad, 5.43 × 10−3 cm−1 for the octad–pentad, and 4.70 × 10−3 cm−1 for the tetradecad–octad hot bands. The resulting new line list will contribute to improve opacity and radiative transfer models for hot atmospheres, such as those of hot-Jupiter type exoplanets.
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Boudon, V., Lamy, M., Dugue-Boyé, F., Pirali, O., Gruet, S., D’Accolti, L., Fusco, C., Annese, C., & Alikhani, M. E. (2016). Synthesis, High-Resolution Infrared Spectroscopy, and Vibrational Structure of Cubane, C8H8. The Journal of Physical Chemistry A, 120(25), 4418–4428.
Résumé: Carbon-cage molecules have generated a considerable interest from both experimental and theoretical points of view. We recently performed a high-resolution study of adamantane (C10H16), the smallest hydrocarbon cage belonging to the diamandoid family (Pirali, O.; et al. J. Chem. Phys. 2012, 136, 024310). There exist another family of hydrocarbon cages with additional interesting chemical properties: the so-called platonic hydrocarbons that comprise dodecahedrane (C20H20) and cubane (C8H8). Both possess C–C bond angles that deviate from the tetrahedral angle (109.8°) of the sp3 hybridized form of carbon. This generates a considerable strain in the molecule. We report a new wide-range high-resolution study of the infrared spectrum of cubane. The sample was synthesized in Bari upon decarboxylation of 1,4-cubanedicarboxylic acid thanks to the improved synthesis of literature. Several spectra have been recorded at the AILES beamline of the SOLEIL synchrotron facility. They cover the 600–3200 cm–1 region. Besides the three infrared-active fundamentals (ν10, ν11, and ν12), we could record many combination bands, all of them displaying a well-resolved octahedral rotational structure. We present here a preliminary analysis of some of the recorded bands, performed thanks the SPVIEW and XTDS software, based on the tensorial formalism developed in the Dijon group. A comparison with ab initio calculations, allowing to identify some combination bands, is also presented.
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Boulet, C., & Ma, Q. (2016). The relaxation matrix for symmetric tops with inversion symmetry. II. Line mixing effects in the ν1 band of NH3. JOURNAL OF CHEMICAL PHYSICS, 144(22), 224304.
Résumé: Line mixing e ects have been calculated in the ν1 parallel band of self-broadened NH3. The theoretical approach is an extension of a semi-classical model to symmetric-top molecules with inversion symmetry developed in the companion paper [Q. Ma and C. Boulet, J. Chem. Phys. 144, 224303 (2016)]. This model takes into account line coupling e ects and hence enables the calculation of the entire relaxation matrix. A detailed analysis of the various coupling mechanisms is carried out for Q and R inversion doublets. The model has been applied to the calculation of the shape of the Q branch and of some R manifolds for which an obvious signature of line mixing e ects has been experimentally demonstrated. Comparisons with measurements show that the present formalism leads to an accurate prediction of the available experimental line shapes. Discrepancies between the exper- imental and theoretical sets of rst order mixing parameters are discussed as well as some extensions of both theory and experiment.
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Coudert, L. H. (2016). The bending potential energy function of HDO obtained from high-resolution data. Journal of Molecular Spectroscopy, 330, 112–119.
Résumé: Line position and line intensity analyses of the high-resolution spectrum of the HDO isotopic species of the water molecule are performed with an extended version of the Bending-Rotation approach up to the (0 1 0) state and J = 22 . The line position analysis involves 3992 microwave, far infrared and infrared lines, and 421 experimental energy levels which were reproduced with a 1.1 unitless standard deviation. The data set considered in the line intensity analysis consists of 1405 infrared absorpon lines and 4 Stark coefficients fitted with a 1.2 unitless standard deviation. The results of both analyses are compared with previous investigations and are used to build a spectroscopic database which is compared with other available databases and should be useful for interpreting measurements carried out with the Infrared Atmospheric Sounding Interferometer (IASI).
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Cuisset, A., Coeur, C., Mouret, G., Ahmad, W., Tomas, A., & Pirali, O. (2016). Infrared spectroscopy of methoxyphenols involved as atmospheric secondary organic aerosol precursors: Gas-phase vibrational cross-sections. Journal of Quantitative Spectroscopy and Radiative Transfer, 179, 51–58.
Résumé: Methoxyphenols are emitted in the atmosphere from biomass burning and recent works have shown the potential role of these oxygenated aromatic species in the formation of secondary organic aerosols. IR spectroscopic data that would enable their remote measurement in the atmosphere remain scarce in the literature. Room temperature Far-IR cross-sections of 4 methoxyphenols (2-methoxyphenol or guaiacol, 3-methoxyphenol, 4-methoxyphenol and 2,6-dimethoxyphenol or syringol) have been determined using the THz synchrotron radiation available at SOLEIL. Mid- and near-IR regions have also been investigated with a conventional Fourier transform IR setup and allowed to provide a set of vibrational cross-sections of the studied methoxyphenols. Finally, gas-phase cross sections of two nitroguaiacol isomers (4-nitroguaiacol and 5-nitroguaiacol), two intermediate products involved in the formation of secondary organic aerosols have been measured in the mid- and near-IR with a heated multi-pass cell. Harmonic and anharmonic density functional theory calculations were carried out for all the studied compounds and allowed a full assignment of the recorded rovibrational bands.
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Depauw, A., Dossi, E., Kumar, N., Fiorini-Debuisschert, C., Huberfeld, G., Ha-Thi, M. - H., Rouach, N., & Leray, I. (2016). A Highly Selective Potassium Sensor for the Detection of Potassium in Living Tissues. Chem. Eur. J., 22(42), 14902–14911.
Résumé: The development of highly selective sensors for potassium is of great interest in biology. Two new hydrosoluble potassium sensors (Calix-COU-Alkyne and Calix-COU-Am) based on a calix[4]arene bis(crown-6) and an extended coumarin were synthesized and characterized. The photophysical properties and complexation studies of these compounds have been investigated and show high molar extinction coefficients and high fluorescence quantum yields. Upon complexation with potassium in the millimolar concentration range, an increase of one- and two-photon fluorescence emission is detected. A twofold fluorescence enhancement is observed upon excitation at λ=405 nm. The ligands present excellent selectivity for potassium in the presence of various competitive cations in water and in a physiological medium. The photophysical properties are not affected by the presence of a large amount of competing cations (Na+, Ca2+, Mg2+, etc.). Ex vivo measurements on mouse hippocampal slices show that Calix-COU-Alkyne accumulates extracellularly and does not alter the neuronal activity. Furthermore, the sensor can be utilized to monitor slow extracellular K+ increase induced by inhibition of K+ entry into the cells.
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Desrier, A., Romanzin, C., Lamarre, N., Alcaraz, C., Gans, B., Gauyacq, D., Liévin, J., & Boyé-Péronne, S. (2016). Experimental and ab initio characterisation of HC3N+ vibronic structure: I-Synchrotron-based Threshold Photo-Electron Spectroscopy. JOURNAL OF CHEMICAL PHYSICS, 145, 234310.
Résumé: Threshold-photoionization spectroscopy of cyanoacetylene (HC3N) and its 15N isotopologue has been investigated in the vacuum-ultraviolet range with a synchrotron- based experiment allowing to record threshold-photoelectron spectrum and photoion yield over a large energy range (from 88500 to 177500 cm−1, i.e. from 11 to 22 eV). Adiabatic ionization energies towards the three lowest electronic states X+ 2Π, A+ 2Σ+ and B+ 2Π are derived from the threshold-photoelectron spectrum. A detailed description of the vibrational structure of these states is proposed leading to the determination of the vibrational frequencies for most modes. The vibrational assignments and the discussion about the electronic structure are supported by multireference ab initio calculations (CASPT2, MRCI). Unprecedented structures are resolved and tentatively assigned in the region of the B+ ← X transition. Exploratory calculations highlight the complexity of the electronic landscape of the cation up to approximately 10 eV above its ground state.
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Falvo, C. (2016). A new interpretation of the meaning of the center of line slope from a two-dimensional infrared spectrum. JOURNAL OF CHEMICAL PHYSICS, 144(23), 234103.
Résumé: This article presents a new approximation to understand the connection between the center of line slope from a single peak of a two-dimensional (2D) infrared spectrum and the frequency-frequency correlation function. This approximation which goes beyond the short-time approximation includes explicitly pure dephasing mechanisms by introducing a time parameter that separates the fast fluctuations and slow fluctuations. While in the short-time approximation, the center of line slope is given by the normalized frequency fluctuations auto-correlation function, I show using this new approximation that the center of line slope measures on long time scales a shifted and scaled correlation function. The results present a new interpretation of the meaning of the center of line slope that allows for a better understanding of what 2D experiments can measure. To illustrate these findings, I compare this approximation with the short-time approximation for several examples of frequency-frequency correlation functions. I also give an estimate of the value of the time separation parameter for a correlation function with a simple exponential decay.
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Gans, B., Holzmeier, F., Krüger, J., Falvo, C., Röder, A., Lopes, A., Garcia, G. A., Fittschen, C., Loison, J. - C., & Alcaraz, C. (2016). Synchrotron-based valence shell photoionization of CH radical. JOURNAL OF CHEMICAL PHYSICS, 144(20), 204307.
Résumé: We report the first experimental observations of X+ 1Σ+ ← X 2Π and a+ 3Π ← X 2Π single-photon ionization transitions of the CH radical performed on the DESIRS beamline at the SOLEIL synchro- tron facility. The radical was produced by successive hydrogen-atom abstractions on methane by uorine atoms in a continuous microwave discharge ow tube. Mass-selected ion yields and photo- electron spectra were recorded as a function of photon energy using a double imaging photoelec- tron/photoion coincidence spectrometer. The ion yield appears to be strongly a ected by vibrational and electronic autoionizations, which allow the observation of high Rydberg states of the neutral species. The photoelectron spectra enable the rst direct determinations of the adiabatic ionization potential and the energy of the rst triplet state of the cation with respect to its singlet ground state. This work also brings valuable information on the complex electronic structure of the CH radical and its cation and adds new observations to complement our understanding of Rydberg states and autoionization processes.
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Gans, B., Lamarre, N., Broquier, M., Liévin, J., & Boyé-Péronne, S. (2016). Experimental and ab initio characterisation of HC3N+ vibronic structure: II- High-resolution VUV PFI-ZEKE spectroscopy. JOURNAL OF CHEMICAL PHYSICS, 145, 234309.
Résumé: VUV pulsed-field-ionization zero-kinetic-energy photoelectron spectra of X+ 2Π ←X 1Σ+ and B+ 2Π ← X 1Σ+ transitions of the HC14N and HC15N isotopologues of cyanoacetylene have been recorded. The resolution of the photoelectron spectra allowed to resolve the vibrational structures and the spin-orbit splittings in the
cation. Accurate values of the adiabatic ionization potentials of the two isotopologues (E /hc(HC14N) = 93909(2) cm−1 and E /hc(HC15N) = 93912(2) cm−1), the vibrational frequencies of the ν2, ν6, and ν7 vibrational modes, and the spin-orbit coupling constant (ASO = −44(2) cm−1) of the X+ 2Π cationic ground state have been derived from the measurements. Using ab initio calculations, the unexpected structure of the B+ 2Π ← X 1Σ+ transition is tentatively attributed to a conical intersection between the A+ and B+ electronic states of the cation.
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Gavilan, L., Alata, I., Le, K. C., Pino, T., Giuliani, A., & Dartois, E. (2016). VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction. A&A, 586, A106.
Résumé: Context. A full spectral characterization of carbonaceous dust analogs is necessary to understand their potential as carriers of observed astronomical spectral signatures such as the ubiquitous UV bump at 217.5 nm and the far-ultraviolet (FUV) rise common to interstellar extinction curves.
Aims. Our goal is to study the spectral properties of carbonaceous dust analogs from the FUV to the mid-infrared (MIR) domain. We seek in particular to understand the spectra of these materials in the FUV range, for which laboratory studies are scarce.
Methods. We produced analogs to carbonaceous interstellar dust encountered in various phases of the interstellar medium: amorphous hydrogenated carbons (a-C:H), for carbonaceous dust observed in the diffuse interstellar medium, and soot particles, for the polyaromatic component. Analogs to a-C:H dust were produced using a radio-frequency plasma reactor at low pressures, and soot nanoparticles films were produced in an ethylene (C2H4) flame. We measured transmission spectra of these thin films (thickness <100 nm) in the far-ultraviolet (190−250 nm) and in the vacuum-ultraviolet (VUV; 50−190 nm) regions using the APEX chamber at the DISCO beam line of the SOLEIL synchrotron radiation facility. These were also characterized through infrared microscopy at the SMIS beam line.
Results. We successfully measured the transmission spectra of these analogs from λ = 1 μm to 50 nm. From these, we extracted the laboratory optical constants via Kramers-Kronig inversion. We used these constants for comparison to existing interstellar extinction curves.
Conclusions. We extend the spectral measurements of these types of carbonaceous analogs into the VUV and link the spectral features in this range to the 3.4 μm band. We suggest that these two materials might contribute to different classes of interstellar extinction curves.
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Gruet, S., Pirali, O., Goubet, M., Tokaryk, D. W., & Bréchignac, P. (2016). High Resolution Far-Infrared Spectroscopy of N-Substituted Two-Ring Polycyclic Aromatic Hydrocarbons: an Extended Study. Journal of Physical Chemistry A, 120(1), 95–105.
Résumé: Polycyclic aromatic hydrocarbons (PAHs) and their N-substituted derivatives are among the largest species for which gas-phase high-resolution spectroscopy can be performed nowadays. In this paper we report the observation and analysis of spectra from several N-substituted two-ring PAHs, all taken in the “fingerprint” far-infrared region (< 850 cm-1). Together with accurate measurements of their pure rotational transitions in the millimeter and sub-millimeter ranges, these synchrotron-based Fourier Transform InfraRed (FTIR) measurements provide an accurate description of the rotational energy levels in the ground and low-energy excited vibrational states of these species. To complement the experimental data, anharmonic DFT calculations were performed to obtain relatively accurate rotational and vibrational parameters. The calculated results strongly support the rotational analysis and provide a good estimate of the equilibrium structures for each species. Extended measurements, analysis and calculations are presented here for the far-IR bands of quinoline (C9H7N), isoquinoline (C9H7N), quinoxaline (C8H6N2), quinazoline (C8H6N2), [1,5]-naphthyridine (C8H6N2), [1,6]-naphthyridine (C8H6N2) and indole (C8H7N) molecules.
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Hartmann, J. - M., Landsheere, X., Boulet, C., Sarkisyan, D., Sarkisyan, A. S., Leroy, C., & Pangui, E. (2016). Infrared look at the spectral effects of submicron confinements of CO_2 gas. Physical Review A, 93(1), 012516.
Résumé: We have recorded, near 4.3 μm, transmission spectra of pure CO2 gas inserted between the windows of an extremely thin absorption cell. This was done for three pressures using a Fourier transform spectrometer and five optical paths between 0.17 and 1.15 μm. For these conditions, the line broadening induced by molecule-surface collisions can be studied under “clean” confinement conditions, i.e., between two parallel well-polished crystal surfaces separated by a known distance. This is in opposition with previous investigations using porous materials which involve pores of unknown dimensions with corrugated inner surfaces of ill-defined shapes. The analysis of the spectra shows that the line broadening due to the collisions of the molecules with the cell windows is independent of the optical transition and inversely proportional to the confinement length. Furthermore, the measured values are quantitatively reproduced if one assumes that a single CO2-surface collision is sufficient to interrupt the rotating-dipole coherence. This gives a proof, here for the CO2-sapphire system, of an assumption proposed many years ago and opens promising perspectives for the optical probing of porous materials.
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Jacquinet-Husson, N., Armante, R., Scott, N. A., Chédin, A., Crépeau, L., Boutammine, C., Bouhdaoui, A., Crevoisier, C., Capelle, V., Boonne, C., Poulet-Crovisier, N., Barbe, A., Chris Benner, D., Boudon, V., Brown, L. R., Buldyreva, J., Campargue, A., Coudert, L. H., Devi, V. M., Down, M. J., Drouin, B. J., Fayt, A., Fittschen, C., Flaud, J. - M., Gamache, R. R., Harrison, J. J., Hill, C., Hodnebrog, Ø., Hu, S. - M., Jacquemart, D., Jolly, A., Jiménez, E., Lavrentieva, N. N., Liu, A. - W., Lodi, L., Lyulin, O. M., Massie, S. T., Mikhailenko, S., Müller, H. S. P., Naumenko, O. V., Nikitin, A., Nielsen, C. J., Orphal, J., Perevalov, V. I., Perrin, A., Polovtseva, E., Predoi-Cross, A., Rotger, M., Ruth, A. A., Yu, S. S., Sung, K., Tashkun, S. A., Tennyson, J., Tyuterev, V. G., Vander Auwera, J., Voronin, B. A., & Makie, A. (2016). The 2015 edition of the GEISA spectroscopic database. New Visions of Spectroscopic Databases, Volume II, 327, 31–72.
Résumé: The GEISA database (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information) has been developed and maintained by the ARA/ABC(t) group at LMD since 1974. GEISA is constantly evolving, taking into account the best available spectroscopic data. This paper presents the 2015 release of GEISA (GEISA-2015), which updates the last edition of 2011 and celebrates the 40th anniversary of the database. Significant updates and additions have been implemented in the three following independent databases of GEISA. The “line parameters database” contains 52 molecular species (118 isotopologues) and transitions in the spectral range from 10−6 to 35,877.031 cm−1, representing 5,067,351 entries, against 3,794,297 in GEISA-2011. Among the previously existing molecules, 20 molecular species have been updated. A new molecule (SO3) has been added. HDO, isotopologue of H2O, is now identified as an independent molecular species. Seven new isotopologues have been added to the GEISA-2015 database. The “cross section sub-database” has been enriched by the addition of 43 new molecular species in its infrared part, 4 molecules (ethane, propane, acetone, acetonitrile) are also updated; they represent 3% of the update. A new section is added, in the near-infrared spectral region, involving 7 molecular species: CH3CN, CH3I, CH3O2, H2CO, HO2, HONO, NH3. The “microphysical and optical properties of atmospheric aerosols sub-database” has been updated for the first time since 2003. It contains more than 40 species originating from NCAR and 20 from the ARIA archive of Oxford University. As for the previous versions, this new release of GEISA and associated management software facilities are implemented and freely accessible on the AERIS/ESPRI atmospheric chemistry data center website.
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Kutzer, P., Weismann, D., Waßmuth, B., Pirali, O., Roy, P., Yamada, K. M. T., & Giesen, T. F. (2016). Far-infrared spectra of dimethyl-ether and its 13C enriched isotopologues: The fundamental band of the C–O–C in plane bending mode, ν7. Journal of Molecular Spectroscopy, 329, 28–34.
Résumé: We recorded the ν 7 fundamental band of dimethyl-ether around 400 cm−1 for the normal and 13C-enriched isotopologues using the Fourier transform spectrometer at the SOLEIL Synchrotron facility. For all three species P, Q and R branch-transitions up to J = 20 and K a = 5 were assigned and the band origins and rotational parameters of Watson’s A-reduced Hamiltonian have been determined by the least-squares fitting procedure. The line splitting due to the torsional tunneling is observed for low J transitions, which is attributed to the ro-vibrational interaction with the excited torsional states.
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Lamarre, N., Gans, B., Vieira Mendes L.A., Gronowski, M., Guillemin, J. - C., de Oliveira N., Douin, S., Chevalier, M., Crépin, C., Kolos, R., & Boyé-Péronne, S. (2016). Excited electronic structure of methylcyanoacetylene probed by VUV Fourier-transform absorption spectroscopy. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 182, 286–295.
Résumé: High resolution photoabsorption spectrum of gas-phase methylcyanoacetylene (CH3C N) has been recorded from 44 500 to 130 000 cm-1 at room temperature with a vacuum ultraviolet Fourier-transform spectrometer on the DESIRS synchrotron beamline (SOLEIL). The absolute photoabsorption cross section in this range is reported for the first time. Valence shell transitions and Rydberg series converging to the ground state X+ 2E of the cation as well as series converging to electronically excited states (A+ 2 A1 and C+) are observed and assigned. Time-dependent density-functional-theory calculations have been performed to support the assignment of the experimental spectrum in the low energy range. A tentative scaling of the previously measured CH3C3N ion yield by Lamarre et al. [17] is proposed, based on the comparison of the absorption data above the first ionization potential with the observed autoionization structures.
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Landsheere, X., Pangui, E., Boulet, C., & Hartmann, J. - M. (2016). Reflection spectroscopy study of the 16O12C16O -band lines. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 174, 1–6.
Résumé: Abstract
Reflection spectra of pure CO2 gas have been recorded in the 4.3 μ m region by using a high resolution Fourier transform spectrometer, providing measured values of the refractive index. Comparisons with the results of calculations using available spectroscopic data, and free of any adjusted line parameter, show a very good agreement. This confirms that this experimental technique provides an alternative approach for the test or determination of spectroscopic parameters. Its advantages for studies of extremely strongly absorbing species and investigations of spatially (tightly) confined molecular gases are discussed.
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Lauzin, C., Gans, B., & Merkt, F. (2016). High-resolution photoelectron-spectroscopic investigation of the H2O+ cation in its A+ electronic state. Molecular Physics, 114(22), 3319–3327.
Résumé: The photoelectron pectrum of water has been recorded in the vicinity of the transition between 112000 and 116000 cm-1 (13.89-14.38 eV). The high resolution allowed the observation of the rotational structure of several bands. Rotational assignments of the transitions involving the Pi(080), Σ(070) and Pi(060) vibronic states of the A+ electronic state are deduced from previous studies of the A+-X+ band system of H2O+ and photoionisation selection rules. The transition to the Σ(030) vibronic state is tentatively assigned.
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Lefebvre-Brion, H., & Kalemos, A. (2016). Interpretation of the predissociation of the CO Rydberg W (1)Pi (v = 1) level. J Chem Phys, 144(13), 134302.
Résumé: With the goal to interpret the experimental results obtained quite recently by Heays et al. [J. Chem. Phys. 141, 144311 (2014)] on the predissociation of the Rydberg W (1)Pi (v = 1) vibrational level of the CO molecule, we report herein ab initio potential energy curves of some of its valence and Rydberg states of both (1)Pi and (3)Pi symmetry. Our results confirm that the above vibrational level is perturbed by a new electronic (1)Pi state not observed until now. They correctly reproduce the linewidths of predissociation of the two interacting levels.
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Lefebvre-Brion, H., & Kalemos, A. (2016). Note: Calculation of the branching ratios for the predissociation of the Rydberg CO W(1)Pi(v=1) level. J Chem Phys, 145(16), 166102.
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Lefebvre-Brion, H., Liebermann, H. P., Amero, J. M., & Vazquez, G. J. (2016). Rydberg, valence, and ion-pair quintet states of O2. J Chem Phys, 144(14), 144302.
Résumé: We report an ab initio study of the quintet states of molecular oxygen. The calculations are carried out employing the multireference single and double excitation configuration interaction package. Potential energy curves of the six quintet valence states dissociating into ground state atoms and of the four quintet states dissociating to ion-pair atoms were computed. A number of bound quintet Rydberg series converging to the a(4)Piu and b(4)Sigmag(-) states of the O2(+) cation have been identified.
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Ma, Q., & Boulet, C. (2016). The relaxation matrix for symmetric tops with inversion symmetry. I. Effects of line coupling on self-broadened ν1 and pure rotational bands of NH3. JOURNAL OF CHEMICAL PHYSICS, 144(22), 224303.
Résumé: The Robert-Bonamy formalism has been commonly used to calculate half-widths and shifts of spectral lines for decades. This formalism is based on several approximations. Among them, two have not been fully addressed: the isolated line approximation and the neglect of coupling between the translational and internal motions. Recently, we have shown that the isolated line approximation is not necessary in developing semi-classical line shape theories. Based on this progress, we have been able to develop a new formalism that enables not only to reduce uncertainties on calculated half-widths and shifts, but also to model line mixing e ects on spectra starting from the knowledge of the intermolecular potential. In our previous studies, the new formalism had been applied to linear and asymmetric-top molecules. In the present study, the method has been extended to symmetric-top molecules with inversion symmetry. As expected, the inversion splitting induces a complete failure of the isolated line approximation. We have calculated the complex relaxation matrices of self- broadened NH3. The half-widths and shifts in the ν1 and the pure rotational bands are reported in the present paper. When compared with measurements, the calculated half-widths match the experimental data very well, since the inapplicable isolated line approximation has been removed. With respect to the shifts, only qualitative results are obtained and discussed. Calculated o -diagonal elements of the relaxation matrix and a comparison with the observed line mixing e ects are reported in the companion paper (Paper II).
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Margulès, L., Martin-Drumel, M. A., Pirali, O., Bailleux, S., Wlodarczak, G., Roy, P., Roueff, E., & Gerin, M. (2016). Terahertz spectroscopy of the 15NH2 amidogen radical⋆. A&A, 591, A110.
Résumé: Context. The determination of isotopic ratios in interstellar molecules is a powerful probe of chemical routes leading to their formation. In particular, the 14N/15N abundance ratio of nitrogen-bearing species provides information on possible fractionation mechanisms. Up to now there is no accurate determination of this ratio in the interstellar medium (ISM) for the amidogen radical, NH2.
Aims. This work is aimed at determining rotational frequencies of 15NH2 to enable its astronomical detection, which will help to understand the formation mechanisms of nitrogen hydrides in the ISM.
Methods. We performed complementary measurements using both synchrotron-based, broadband far-infrared and high-resolution, submillimeter-wave frequencies to investigate the pure rotational spectrum of the 15NH2 species.
Results. The first spectroscopic study of the 15N-isotopologue of the amidogen radical yielded an accurate set of molecular parameters.
Conclusions. Accurate frequencies are now available for 15NH2 up to 7 THz (with N′′ ≤ 13) allowing dedicated astronomical searches to be undertaken.
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Martin-Drumel, M. A., Roucou, A., Brown, G. G., Thorwirth, S., Pirali, O., Mouret, G., Hindle, F., McCarthy, M. C., & Cuisset, A. . (2016). High resolution spectroscopy of six SOCl2 isotopologues from the microwave to the far-infrared. JOURNAL OF CHEMICAL PHYSICS, 144(8), 084305.
Résumé: Despite its potential role as an atmospheric pollutant, thionyl chloride, SOCl2, remains poorly characterized in the gas phase. In this study, the pure rotational and ro-vibrational spectra of six isotopologues of this molecule, all detected in natural abundance, have been extensively studied from the cm-wave band to the far-infrared region by means of three complementary techniques: chirped-pulse Fourier transform microwave spectroscopy, sub-millimeter-wave spectroscopy using frequency multiplier chain, and synchrotron-based far-infrared spectroscopy. Owing to the complex line pattern which results from two nuclei with non-zero spins, new, high-level quantum-chemical calculations of the hyperfine structure played a crucial role in the spectroscopic analysis. From the combined experimental and theoretical work, an accurate semi-experimental equilibrium structure of SOCl2 has been derived. With the present data, spectroscopy-based methods can now be applied with confidence to detect and monitor this species, either by remote sensing or in situ.
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Pearson, J. C., Yu S., & Pirali O. (2016). Modeling the spectrum of the 2 nu(2) and nu(4) states of ammonia to experimental accuracy. JOURNAL OF CHEMICAL PHYSICS, 145(12), 124301.
Résumé: The vibrational spectrum of ammonia has received an enormous amount of attention due to its potential prevalence in hot exo-planet atmospheres and persistent challenges in assigning and modeling highly excited and often highly perturbed states. Effective Hamiltonian models face challenges due to strong coupling between the large amplitude inversion and the other small amplitude vibrations. To date, only the ground and ν2 positions could be modeled to experimental accuracy using effective Hamiltonians. Several previous attempts to analyze the 2ν2 and ν4 energy levels failed to model both the microwave and infrared transitions to experimental accuracy. In this work, we performed extensive experimental measurements and data analysis for the 2ν2 and ν4 inversion-rotation and vibrational transitions. We measured 159 new transition frequencies with microwave precision and assigned 1680 new ones from existing Fourier transform spectra recorded in Synchrotron SOLEIL. The newly assigned data significantly expand the range of assigned quantum numbers; combined with all the previously published high-resolution data, the 2ν2 and ν4 states are reproduced to experimental accuracy using a global model described here. Achieving experimental accuracy required inclusion of a number of terms in the effective Hamiltonian that were neglected in previous work. These terms have also been neglected in the analysis of states higher than 2ν2 and ν4 suggesting that the inversion-rotation-vibration spectrum of ammonia may be far more tractable to effective Hamiltonians than previously believed.
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Schubert, A., Falvo, C., & Meier, C. (2016). Mixed quantum-classical simulations of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein. JOURNAL OF CHEMICAL PHYSICS, 145(5), 054108.
Résumé: We present mixed quantum-classical simulations on relaxation and dephasing of vibrationally excited carbon monoxide within a protein environment. The methodology is based on a vibrational surface hopping approach treating the vibrational states of CO quantum mechanically, while all remaining degrees of freedom are described by means of classical molecular dynamics. The CO vibrational states form the “surfaces” for the classical trajectories of protein and solvent atoms. In return, environmentally induced non-adiabatic couplings between these states cause transitions describing the vibrational relaxation from first principles. The molecular dynamics simulation yields a detailed atomistic picture of the energy relaxation pathways, taking the molecular structure and dynamics of the protein and its solvent fully into account. Using the ultrafast photolysis of CO in the hemoprotein FixL as an example, we study the relaxation of vibrationally excited CO and evaluate the role of each of the FixL residues forming the heme pocket.
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Sung, K., Yu, S., Pearson, J., Pirali, O., Kwabia Tchana, F., & Manceron, L. (2016). Far-infrared 14NH3 line positions and intensities measured with a FT-IR and AILES beamline, Synchrotron SOLEIL. New Visions of Spectroscopic Databases, Volume II, 327, 1–20.
Résumé: Abstract
Extensive measurements of line positions and intensities are reported for the inversion-rotation and rovibrational transitions of 14NH3 in the 50–660 cm−1 region. This study analyzes high-resolution (0.00167 cm−1, unapodized) Fourier-transform spectra of high purity (99.5%) normal ammonia sample obtained using the AILES beamline of Synchrotron SOLEIL. The experimental conditions are designed to study transitions with intensities weaker than 1 × 10−22 cm−1/(molecule cm−2) at room temperature. Line positions and intensities of more than 2830 transitions of 14NH3 are measured and compiled after proper quality control; the features from minor isotopologues (15NH3 and NH2D) and H2O are identified and excluded. Based on the predictions of recent work from the empirical Hamiltonian modeling, systematic quantum assignments are made for 2047 transitions from eight bands including four inversion-rotation (gs, v2, 2v2, and v4) and four ro-vibrational bands (v2–gs, 2v2–v2, v4–v2, and 2v2–v4), as well as covering their ΔK = 3 forbidden transitions. The measured line positions for the assigned transitions are in an excellent agreement (typically better than 0.001 cm−1) with the predictions in a wide range of J and K for all the eight bands. The comparison with the HITRAN 2012 database is also satisfactory, although systematic offsets are seen for transitions with high J and K and those from weak bands. Also we note that out of the eight bands, the 2v2–v4 has not been listed in the HITRAN 2012 database. Differences of 20% are seen between our measured and calculated intensities depending on the bands. For line positions, greater differences are found for some NH3 bands in HITRAN 2012 than recent predictions. Measurements of the individual line positions and intensities are presented for the eight bands, and the final spectroscopic line positions and intensities are compiled as an electronic supplement.
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Thorwirth, S., Martin-Drumel, M. A., Endres, C. P., Salomon, T., Zingsheim, O., van Wijngaarden, J., Pirali, O., Gruet, S., Lewen, F., Schlemmer, S., & McCarthy, M. C. (2016). An ASAP treatment of vibrationally excited S2O: The ν3 mode and the ν3 + ν2 − ν2 hot band. Journal of Molecular Spectroscopy, 319, 47–49.
Résumé: Abstract
The fundamental S–S stretching mode ν3 of disulfur monoxide, S2O, located at 679 cm−1, has been investigated using Fourier-transform far-infrared spectroscopy at the SOLEIL synchrotron facility. A spectroscopic analysis has been performed using an Automated Spectral Assignment Procedure (ASAP) which permits accurate determination of more than 2000 energy levels from ν3. In addition, the ν3 + ν2 − ν2 hot band was observed for the first time and some 500 corresponding energy levels were assigned. The high-resolution synchrotron study was complemented with pure rotational spectra of S2O in the (v1, v2, v3) = (0, 0, 1) vibrational state observed in the frequency range from 250 to 280 GHz using a long-path absorption cell. From these combined measurements, extensive molecular parameter sets have been determined and precise band centers have been derived for both vibrational bands.
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Vander Auwera, J., Boulet, C., Carré, Y., Kocon, L., & Hartmann, J. - M. (2016). Confinement-induced infrared absorption by H2 and N2 gases in a porous silica aerogel. JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, 182, 193–198.
Résumé: Abstract
Transmission spectra in the fundamental bands of H2 and N2 gas inside the pores of a silica aerogel sample were recorded at room temperature and for several pressures using a Fourier transform spectrometer. They first show that, as the absorption is proportional to the pressure, it is due to the interactions of the molecules with the inner surfaces of the pores and not to the dipole induced during gas-phase molecule–molecule collisions. Furthermore, the analysis of the widths and areas of the observed absorption structures indicate that, for the considered aerogel sample, most of the absorption is likely due to “free” molecules moving within the pores with a weak contribution of adsorbed molecules.
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Chapitres de Livres |
Kumar, N., Qui, P. X., Roopa, Leray, I., & Ha-Thi, M. - H. (2016). Calixarene-Based Fluorescent Molecular Sensors. In Reference Module in Chemistry, Molecular Sciences and Chemical Engineering. Elsevier.
Résumé: In this present article, we present recent development of fluorescent molecular sensors based on calixarene for the detection of various species including cations, anions, and neutral molecules. The observed modulation of the fluorescence is because of perturbation of several photoinduced processes such as electron transfer, energy transfer, charge transfer, excimer formation and disappearance, chemodosimeter, and aggregation effect. The discussion clearly indicates the role of calixarene framework in developing selective and sensitive molecular sensor for a particular type of analyte.
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