Relaxation of Nitric Oxide in Mixtures with Argon

Abstract

The variation of the relaxation rate of the rotational, electronic, and vibrational degrees of freedom of the nitric oxide molecule with the amount of argon admixed has been investigated by acoustic absorption measurements. The rotational and electronic relaxation show small influence of the argon content, so NO-Ar and NO-NO collisions are of similar efficiency in the deexcitation of the rotational and electronic degrees of freedom. In contrast to this, the measurements show a much lower vibrational transition probability for heteromolecular collisions as compared with the homomolecular ones. This confirms the assumption of a specific NO-NO interaction with respect to vibrational deexcitation that could result from the chemical affinity of two NO molecules.