6533b854fe1ef96bd12afa36

RESEARCH PRODUCT

Etude théorique de spectres de molécules toupies sphériques à l'aide du formalisme d'ensembles tensoriels irréductibles

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description

Vibrational-rotational spectroscopy of molecules of the spherical top type, in particular, SiH4 and GeH4 molecules, as well as their isotopologues, is of interest in various fields of science and technology, especially in astrophysics and planetology. One of the most important discoveries in the study of the atmospheres of giant planets is the discovery of german and silane gases in the atmospheres of Saturn, Titan, and Jupiter. Despite many years of research on the vibrational-rotational spectra of molecules of german, silane, and their deuterated modifications, many spectral ranges are still unexplored. However, a complete study of the atmospheres of giant planets is possible only in the presence of spectroscopic information about all possible spectral ranges. Consequently, the study of the vibrational-rotational spectra of these molecules and the extraction of high-precision spectroscopic information from them, namely, on the characteristics of spectral lines (line positions, intensities, broadening coefficients, and pressure shifts) from experimental data, is currently an urgent task. Therefore, this work aims to study the spectra of molecules of the XY4 type based on irreducible tensor operators.The first part of the thesis is devoted to studying the fine vibrational-rotational structure of the spectra of five isotopologues of the german molecule MGeH4 (M = 70, 72, 73, 74, 76). As a result, a wide spectral range of the Dyad, Pentad, Tetradecad, and Octad was studied. More than 20000 transitions have been analyzed, corresponding to about 8500 vibrational-rotational energies for 28 vibrational states. Based on the line-shape approximation of the experimental lines by the Hartmann–Tran profile, the line strengths of more than 2000 lines of four vibrational bands were determined. The line shapes of two bands of all five germane isotopologues are analyzed for the first time. The self-broadening coefficients and line shifts are obtained. The second part of the thesis is devoted to studying the fine vibrational-rotational structure of the spectra of three isotopologues of the MSiD4 silane molecule (M = 28, 29, 30). A special analysis of the evaluation of the band centers was carried out. The initial values ​​of the main spectroscopic parameters and shifts of the band centers in the case of isotopic substitution of nuclei for the SiD4 molecule are calculated. Preliminary estimates of the spectroscopic parameters in the study of absorption spectra in the short-wavelength regions, which are more difficult to analyze, make it possible to correctly predict vibrational energies for SiH4 and SiD4 molecules. The ranges of the Dyad and Pentad, including 10 vibrational bands, were studied. In total, more than 14000 transitions have been analyzed, which corresponds to about 5000 energies for 10 vibrational states. As a result of the study, sets of spectroscopic parameters were determined, namely, the parameters of centrifugal distortion, resonant interactions, and tetrahedral splittings, which describe 10 vibrational states with an accuracy comparable to experimental uncertainty.