BAND SHAPE OF Q-BRANCHES OF PARALLEL BANDS OF SYMMETRICAL-TOP MOLECULES

Abstract

The analysis of Q-branches may proceed by the following three stages: a band shape measurement, the sequence treatment, and finally the fine structure analysis. Either of these will provide information on the change of moment of inertia due to the vibrational states. The fine structure of the Q-branch of the $2200 cm^{-1}$ frequency of $CH_{3}$D molecule is calculated and compared with the experimental measurements obtained by Boyd and $Thompson.^{1}$ The conclusion is that the value of ($A^{\prime}-A^{\prime\prime} -B^{\prime} + B^{\prime\prime}) = 0.0406$ cm$^{-1}$ which was obtained from the P-branch analysis, is better than 0.0372 cm$^{-1}$ obtained by the R-branch, if the values of other parameters are assumed to be those by him. Next, the sequence structure of Q-branch is discussed. Finally, a method of calculation of the band shape is presented by the assumption that the summation over J and K is approximated by an integration. The result of the calculation by this assumption is compared with the observed for some molecules.