INFRARED BAND SHAPES II. CORIOLIS COUPLING IN DEGENERATE MODES

Abstract

A general quantitative treatment has been made of the influence of Coriolis vibration-rotation interactions on the shapes of infrared band envelopes of symmetric and spherical top molecules. The band envelopes have been computed from theory with the aid of an IBM-card-programmed digital computer. The problem has been so programmed that the decks of cards may be adapted to any molecule by changing only the two cards which introduce the Coriolis coupling parameter and the ratios of the moments of inertia. Since these decks are easily duplicated, they will be available to others having access to a similar IBM computer. The results are presented in the form of a table of curves for nine values of the coupling parameter and nine ratios of the moments of inertia. The computed contours exhibit a pronounced dependence on the extent of the coupling, and in favorable cases the coupling parameter can be evaluated, at least approximately, by comparison of the experimental and computed band envelopes. This has been done for several molecules, and the results are in agreement with the appropriate sum rule. For example: $NF_{3}$:$\zeta_{3}=.78, \zeta_{4}=-.87$ sum rule $-.08$; $CF_{4}$:$\zeta_{3}=.83, \zeta_{4}=-.35$ sum rule .50.