The vibrational relaxation of H 2. II. Measured density changes; master equation study of the mechanism of relaxation

Abstract

The vibrational relaxation of H 2 in mixtures with inert gases has been studied in shock waves, using laser schlieren densitometry. The measured total density changes corresponding to the observed relaxation are too large to be accounted for by changes in vibrational energy alone. It is suggested that the rotational degrees of freedom of H 2 participate in the relaxation process. This is confirmed by master equation studies of the relaxation mechanism, which indicate that an important role is played by transitions involving simultaneous changes in rotational and vibrational energy.