Knowledge Bank

The FT=IR $spectrum1$ of the $v4$ band of $SF6(615$ $cm-1)$ obtained at room temperature reveals that the R-branch has 27% more absorption intensity than the P-branch. This inbalance is substantially larger than the 15% excess predicted by rotational statistics and the non-negligible width of the band. This shift in intensity is a consequence of perturbations on the rovibrational line intensities, from Coriolis interactions between the $v4$ and $v3$ excited states, and also between the ground and combination $v3+v4$ states. Such perturbations can be expressed using a superposed Herman-wall is F-factor of the form $$F(m) = (1+\xi m)^{2}$$, as in some bands of $CH42$ and $CO2.3$ We have derived an experimental value for $\xi$; using a new formalism involving total branch intensities. Model intensity calculations for the perturbed $\nu$3 band in $SF6$ will be discussed, and estimations will be presented for the $v3$ and $v4$ bands of $UF6$. Finally, weak Coriolis enabling of the normally inactive $v6$ mode is predicted and estimated.