MOLECULAR ROTATION AND KINETIC COLLISIONS - A SYSTEMATIC STUDY OF CH3F IN THE NU(4) BAND

In order to determine the effect of molecular rotation on gas kinetic collisions, light-induced drift measurements were performed on CH3F in the nu(4) rovibrational band. Data were taken for a large set of tran sitions of the type v = 0 --> 1, Delta J = 1, Delta K = 1 over a range of values of J or K. Systematic trends in the J- and K-dependence of the kinetic collision rate have been observed. For Kr and CH3Cl as col lision partners the K-dependence is found to be large and nearly linea r in K, whereas the J-dependence is found to be small. We present a th eoretical model to describe the dependence on the rotational quantum n umbers of the relative change in collision rate upon excitation; this model is in satisfying agreement with the experimental results.