Coriolis intensity perturbations of the ν_{4} band of SF _{6}
Abstract
In the ν_{4} band of ^{32}SF _{6} the intensity of absorption by the R branch has been found to exceed that of the P branch by 38%. This is substantially larger than the 15% excess that one calculates from ordinary rotational statistics and the nonnegligible width of the band. We attribute this imbalance to Coriolis interactions between the rovibrational sublevels (a) of the ν_{3} and ν_{4} excited vibrational states, and (b) of the ground vibrational state and the l = 1 ( F_{1 g}) level of the ν_{3} + ν_{4} combination state. The intensities of the observed P and Rbranch lines have a superposed HermanWallis type F factor of the form F( m) = (1 + ξ _{4}m) ^{2}, where m =  J for the P branch, 0 for the Q branch, and +( J + 1) for the R branch, and J is the rotational sublevel in the ground state. We have determined ξ _{4} by a new method from the relative intensities of the P, Q, and R branches. New evidence is reported that supports an earlier conclusion that the first derivatives of the dipole moment function, μ _{3} = {∂μ}/{∂q _{3}} and μ _{4} = {∂μ}/{∂q _{4}}, have the same sign. The corresponding Coriolis effect is calculated for UF _{6}. It is predicted that Coriolis interactions induce weak absorption in the ν_{6} bands of SF _{6} and UF _{6}, which would otherwise be inactive according to selection rules for strong infrared absorption or Raman scattering. An orderofmagnitude estimate of the absorption intensity of the induced ν_{6} band of SF _{6} agrees with a recent observation of that infrared spectral region.
 Publication:

Journal of Molecular Spectroscopy
 Pub Date:
 March 1983
 DOI:
 10.1016/00222852(83)902175
 Bibcode:
 1983JMoSp..98..229P