Experimental and Theoretical Study of the V yields T,R Relaxation of CD4 between 300 and 100K

摘要

The values of the rate constants for the relaxation of the lowest vibrational modes of methane (CH4) and CD4 are of interest as they provide evidence for the relative importance of rotation in these processes. Some data exist for the lowest vibrational modes of CD4 at room temperature and for its self-deactivation between 376 and 140 K. There is, however, a paucity of low-temperature data concerning its deactivation by different collision partners. We have measured rate constants for various collision partners deactivating the bending modes of CD4 between 300 and 100K. The experimental method used is the laser fluorescence technique in which excitation of the bending modes of CD4 is achieved by collisionally pumping CD4 with CO. The results have been interpreted in terms of a theoretical model which is based on SSH theory and therefore calculates the probability of energy transfer per collision. The theory has been modified to include a contribution for the rotational motion of both collision partners in addition to their relative translational motion.