Thérèse Huet

Spectroscopy and vibrational couplings in the 3v3 region of acetylene

14 rovibrational bands are observed in the 1 micron region of the absorption spectrum of C2H2, between 9300 and 10 500 cm-1, and rotationally analysed. Transition induced dipole moments are estimated for all the cold bands involving upper levels of σ u + symmetry. Those various data are used to demonstrate the leading role of the 0030000 level in the vibrational mixings and also to deal quantitatively with a possible picture of the couplings occurring among the cluster of levels in resonance with 0030000.

The bending vibrational levels in C2D2 (X̃ 1Σ+g)

Improved sets of data have been recorded and analyzed in order to study the bending rovibrational energy levels of C2D2, in the regions of the ν5–ν4 difference band (FIR) and of the ν5 fundamental band (IR). A matrix model is setup to deal with a Darling–Dennison coupling between sets of bending levels as well as with the usual l‐type resonances. A simultaneous fit of the new data together with earlier microwave measurements produces an extended set of very accurate parameters, including for the first time in C2D2 s45 and qkt.

L-type resonances in C2H2

A full Hamiltonian matrix coherent with a phase convention leading to e/f labellings and to positive l-doubling q parameters is constructed to describe the rovibrational energy levels in a linear polyatomic molecule with two bending vibrations. This model is used to investigate quantitatively the effect of the rotational and vibrational l resonances on level mixings and intensity features in C2H2.

The à electronic state of acetylene: Geometry and axis-switching effects

Abstract The geometrical parameters concerning acetylene in the A state are derived: r CC = 1.375 A , r CH = 1.097 A , and HCH = 122.48°. New rovibrational parameters of acetylene in the A state are provided or predicted. Axis-switching intensities are discussed on the basis of an extended formulation using the tensor algebra.

The Ã-X̃ band system of C2D2: Vibration-rotation constants for the Ã1Au state

Abstract The analysis of data arising from high-resolution absorption spectra of the A - X band system in C 2 D 2 leads to assignment of 130 out of 135 bands observed between 41 500 and 47 900 cm −1 . New or improved results are obtained for 24 vibrational levels in the A 1 A u electronic state. For the first time rotational constants are presented for the upper state, concerning 19 of those vibrational levels. The analysis of several axis-switching bands is also reported. Perturbations are tentatively assigned in terms of a close-by triplet electronic state.

The (CH2)2O-H2O hydrogen bonded complex. Ab Initio calculations and Fourier transform infrared spectroscopy from neon matrix and a new supersonic jet experiment coupled to the infrared AILES beamline of synchrotron SOLEIL.

A series of hydrogen bonded complexes involving oxirane and water molecules have been studied. In this paper we report on the vibrational study of the oxirane-water complex (CH(2))(2)O-H(2)O. Neon matrix experiments and ab initio anharmonic vibrational calculations have been performed, providing a consistent set of vibrational frequencies and anharmonic coupling constants. The implementation of a new large flow supersonic jet coupled to the Bruker IFS 125 HR spectrometer at the infrared AILES beamline of the French synchrotron SOLEIL (Jet-AILES) enabled us to record first jet-cooled Fourier transform infrared spectra of oxirane-water complexes at different resolutions down to 0.2 cm(-1). Rovibrational parameters and a lower bound of the predissociation lifetime of 25 ps for the v(OH)(b) = 1 state have been derived from the rovibrational analysis of the ν(OH)(b) band contour recorded at respective rotational temperatures of 12 K (Jet-AILES) and 35 K (LADIR jet).

The Ã1A″ electronic state of monodeuterated acetylene

Abstract Eighty-six vibronic subbands of the A - X system of C 2 HD are assigned, in the conventional high-resolution absorption spectrum and in the jet-cooled laser fluorescence excitation spectrum, between 42 200 and 47 000 cm −1 . Transitions involving all six normal modes of vibration in the A state are assigned, leading to the determination of an extensive set of vibrational parameters. Isotopic comparisons are used to predict still unknown vibrational frequencies in the A state of C 2 H 2 and C 2 D 2 .

Levels of the transbending normal mode of vibration in C2D2

Abstract The analysis of data arising from high-resolution absorption spectra of C 2 D 2 in the ultraviolet range leads to results concerning the transbending levels in the ground electronic state. Original rovibrational constants are obtained for 2 ν 4 and 3 ν 4 and vibrational term values are derived for 4 ν 4 .

Low-energy vibrational levels in the Ã1Au electronic state of C2D2

Mesure des spectres dexcitation de fluorescence de lacetylene bideuterie et attribution du systeme A-X~ a laide des constantes rovibrationnelles determinees anterieurement

Synchrotron FTIR spectroscopy of weak torsional bands: A case study of cis-methyl formate

The far infrared spectrum of cis-methyl formate has been recorded on the AILES beamline of the synchrotron SOLEIL using a Fourier transform infrared spectrometer coupled to a long path cell. The very weak fundamental band associated with the methyl-top torsion mode (ν(18)) was observed. The frequency analysis was performed using the rho axis method, and the microwave and millimeter-wave data from the literature. A precise determination of the band origins (ν(18)(A) = 132.4303 cm(-1) and ν(18)(E) = 131.8445 cm(-1)) and of the barrier height [V(3) = 370.7398 (58) cm(-1)] have been obtained. The intensity of the ν(18) fundamental band was determined to be 3.4 × 10(-21) cm(-1)∕(molecule cm(-2)) at 297 K, equally shared among A-A and E-E transitions, thus leading to a dipole moment component μ(c)(3) equal to 0.0483 D. The results were compared with the ab initio calcula-tions of Senent et al. [Astrophys. J. 627, 567 (2005)].