O.V. Gromova

Analysis of highly excited ‘hot’ bands in the SO2 molecule: ν2 + 3ν3 − ν2 and 2ν1 + ν2 + ν3 − ν2

We set up a variational procedure of assignments of transitions and we applied it to the analysis very weak ‘hot’ bands, ν2 + 3ν3 − ν2 and 2ν1 + ν2 + ν3 − ν2, of the SO2 molecule. As the first step of the study, the ‘cold’ bands, 3ν3 and 2ν1 + ν3, are re-analysed and transitions belonging to those bands are assigned up to the values of quantum numbers J max. = 60, , and J max. = 69, for the bands 3ν3 and 2ν1 + ν3, respectively. After ‘cleaning’ the experimental spectrum from transitions belonging to the 3ν3 and 2ν1 + ν3 bands, a variational procedure was used that allowed us to assign 230 and 115 transitions with the values of quantum numbers J max. = 35, , and J max. = 26, for the bands ν2 + 3ν3 − ν2 and 2ν1 + ν2 + ν3 − ν2, respectively. The sets of spectroscopic parameters obtained by fitting the assigned experimental transitions reproduce the initial experimental data with an accuracy close to experimental uncertainties.

On the ‘expanded local mode’ approach applied to the methane molecule: isotopic substitution CH2D2 ←CH4

On the basis of a compilation of the ‘expanded local mode’ model and the general isotopic substitution theory, sets of simple analytical relations between different spectroscopic parameters (harmonic frequencies, ωλ, anharmonic coefficients, x λμ, ro-vibrational coefficients, , different kinds of Fermi- and Coriolis-type interaction parameters) of the CH2D2 molecule are derived. All of them are expressed as simple functions of a few initial spectroscopic parameters of the mother, CH4, molecule. Test calculations with the derived isotopic relations show that, in spite of a total absence of initial information about the CH2D2 species, the numerical results of the calculations have a very good correlation both with experimental data, and results of ab initio calculations.