Rovibrational spectra of DCF3 in the 1900cm−1 region: High-resolution study of the v3=v4=1/v3=2, v6=1 Fermi-interacting levels

International audienceThe degenerate combination levels of E symmetry v3 = v4 = 1 (1900.21 cm−1) and v3 = 2, v6 = 1 (1889.30 cm−1) were investigated for the first time with high-resolution, using a Fourier-transform infrared spectrum recorded in the 1600–2000 cm−1 region, at a resolution of 0.0024 cm−1. These combination levels strongly interact through a Fermi-type anharmonic coupling, which plays an essential role in the studied system. Besides the Fermi-interaction, the other important Coriolis (Δk = ±1, Δl = ∓2) and higher-order (Δk = Δl = ±2) inter-vibrational interactions were also considered, in a similar manner as in the lower ν3 + ν6/ν4 dyad [P. Pracna et al., J. Mol. Spectrosc. 259 (2010) 1–10]. The fitted wavenumbers of the rovibrational transitions of the ν3 + ν4 and 2ν3 + ν6 bands provide a set of molecular parameters which ensure an accurate reproduction of the spectrum. Moreover, these molecular parameters show good agreement with those of the lower system ν3 + ν6/ν4

Phase-space description of a particle in a quartic double-well potential

International audienceThe stationary Wigner functions (WFs) have been calculated for particles evolving in a quartic double-well potential V (x) = ax2/2 + bx4/4 (a \textless 0 and b \textgreater 0), at temperature T. In the high temperature limit, the results totally agree with those obtained using Wigner’s perturbative method of deriving quantum corrections to the classical distribution function. Comparison with the perturbative approach allows one to establish the range of applicability of the latter. For illustration, the second moments of the position and momentum have been calculated for the double-well potential. Furthermore, the time-evolution of the WFs for a state initially located at one of the wells has been also investigated to show the tunneling effect

The 2 ν 6 / ν 2 + ν 3 / ν 3 + ν 5 band system of CH 3 Br revisited: Modeling anharmonic and Coriolis interactions in a three-level system near 2000 cm −1

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Effective Hamiltonians for the Fermi resonance – Interacting states of C3vC3v molecules

International audienceA global reduction theory of the vibration–rotational Hamiltonian of C3v closed-shell molecules, dealing with all possible anharmonic interactions in which a fundamental vibration can be involved, is presented. The effective correlation-free Hamiltonians and the corresponding matrix elements are derived. The cases studied here are (i) a fundamental band interacting with an overtone, (ii) a fundamental band interacting with a combination band. The Hamiltonian terms H30;H31;H32 and the recommended set of parameters following from the appropriate reductions are presented. The results are provided in a form directly applicable to the analysis of spectra of the interacting states

Rovibrational spectra of DCF3 in the 2000cm−1 region: A high-resolution study of the v5=2 and v2=v5=1 levels

International audienceThe high-resolution infrared spectrum of DCF3 was investigated in the 2000 cm-1 region, with the aim of assigning and analyzing the overtone bands 2v5 (A1 + E), as well as the combination band v2 + v5 (E). The present paper reports on the first high-resolution study of the v2 = v5 = 1 and v5 = 2 levels, through the analysis of the combination v2 + v5 and the overtone 2ν5∓2 bands respectively. This analysis can be thought of as a necessary step toward the reinvestigation of the complicated vibrational pattern in the CD stretching fundamental region

Theoretical interpretation of the infrared lineshapes of the H- and D-bonds in liquid formic acid

International audienc

Revised assignments of the v4=1 vibrational level of CH35Cl3: The ν4 and ν4-ν3 rovibrational bands with remarkable clustering effects

International audienc

High-resolution infrared and millimeter-wave spectroscopy of CH35Cl3: The v2=v6=1 combination level

International audienc

Rovibrational fine structure and transition dipole moment of CF3H by frequency-comb-assisted saturated spectroscopy at 8.6 μm

We report on rovibrational fine structure spectroscopy of room-temperature trifluoromethane with a saturated absorption method, using a quantum cascade laser at around 8.6 µm phase-locked to a self-referenced mid-infrared frequency comb synthesizer. The absolute line-center frequencies of 36 lines have been measured by means of the wavelength modulation method with a best fractional uncertainty of 3e-9 in a single acquisition scan from 34.7426 to 34.7443 THz. In addition, an extensive investigation of the measured Lamb-dip profiles using both direct pump-probe spectroscopy method and wavelength modulation technique has been performed for two selected lines, rR40(64) and rR36(38), belonging to the vibrational band, as a function of either the gas pressure or the pump beam power. This approach allowed the measurement of the main spectroscopic parameters, such as saturation intensity, transition electric dipole moment, as well as self-pressure broadening coefficient