Knowledge Bank

We report the results of a detailed study of the rotational-vibrational energy transfer processes in the symmetric top $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3F$. This work has been done by observing in real time the relaxation of the nonthermal population placed in $J=5,K=3$ of the $\nu 3$ vibrational state by a Q-switched $CO2$ laser. Millimeter and submillimeter wave spectroscopic techniques were used as a sensitive diagnostic $probe2$. Energy transfer processes observed include fast rotational relaxation of velocity subsets within $K=3$, transfer of population to other K states via direct $\Delta K=3n$ processes as well as a ``K-swap'' mechanism that transcends the selection rules imposed by spin statistics, the transfer of population to the v6 and other higher lying vibrational states, and the relaxation of the vibrational population. For the vibrational relaxation, both direct molecule-molecule and wall relaxation were observed. In addition, the wall relaxation channel was shown to require several wall collisions. All of these observations have been fit to a global simulation of the population flow within this system. This model accounts for the observed behavior with a small number of molecular parameters, all of which are physically identifiable.