ROTATIONAL DEPENDENCE OF DIAGONAL CORIOLIS COUPLING

The diagonal Coriolis coupling in degenerate vibrational states of symmetric- or spherical-top molecules has a rotational dependence of degree three in the components of the total angular momentum vector. A general formula is obtained for the coefficients of these terms and is specialized to the cases of symmetric tops (particularly C3v molecules), where the coefficients are Maes' constants ηtJ and ηtK, and of cubic spherical tops, where the coefficients are Hecht's constants Ft (t ∈ E), FuS and FuT (u ∈ F1,2). It is shown that these coefficients obey certain sum rules in which many of the contributions cancel. The values of the sums can be expressed in terms of the ordinary quartic centrifugal constants DJ, DJK, and DK for a symmetric top, or D and DT for a cubic spherical top. The sum rules for methane are approximately satisfied by the experimental values of the constants. © 1979.