Knowledge Bank

We have used time-resolved infrared/mm-wave double resonance techniques to study rotational and vibrational collisional processes in methyl chloride. As was the case with $CH3F1$, the dipole-dipole process in $CH3Cl$ has the largest cross section, and the $\Delta J=n,\Delta K=0(n\ge 2)$ processes are well described by a two parameter Statistical Power Gap Law (SPG). In addition, we have measured a rapid $\Delta K=3n$ thermalizing processes in $v6=1$ of $CH3Cl$ similar to that observed in $v3=1$ of $CH3F2$. However, the $\Delta K=3nCH3Cl$ data exhibited a feature distinct from that of the $CH3F$. Whereas the $\Delta K=3n$ process populates the $CH3F$ final states with an ambient temperature Boltzmann distribution, it populates the $CH3Cl$ states with an initially nonambient Boltzmann distribution. This initial temperature is related to the energy of the rotational state populated by the $CO2$ laser pump, and its relaxation rate is related to the rate that the $\Delta K=3n$ process populates the A symmetry (the pumped symmetry) states. The $CH3Cl$ and $CH3F$ results will be reconciled.