Knowledge Bank

Because the frequency of a molecular transition may be written in the form $\nu =\sum 1c1f1(J,K;\Delta J,\Delta K)$, it might at first be expected that a simultaneous least squares solution for the molecular constants $ci$, could be obtained by using all observed transitions. Although this is normally true, complications arise for degenerate bands in which Coriolis coupling is significant. In these cases the form of the frequency expression depends on whether the Coriolis coupling has a doubling or a resonance effect. Therefore, it is convenient to distinguish two different methods of analysis; one to be applied to transitions involving levels which are split, and the other to be applied to transitions involving levels which are shifted. The second method mentioned above has been applied to the analysis of degenerate infrared and Raman bands of $CH3D$ and $CHD3$ using data given in the literature as well as some new data. The values obtained for the Coriolis coupling constants by this method are compared, where possible, to values previously obtained from transitions involving only levels which are split.