On the moments of the pressure-induced spectra of gases

Abstract

It is pointed out that each component of a pressure-induced spectrum has two moments for which there are rigorous theoretical expressions. It is shown how these moments are related to the experimentally observed intensity. The theoretical expressions are given for the translational spectrum of inert gas mixtures and the translational, rotational, and vibrational–rotational spectra of homonuclear diatomic gases and of mixtures of these with inert gases. Examples of analyses in terms of these moments are given for the cases of the translational spectra of He–Ar, Ne–Ar, H2–Ar, H2–Kr, and H2–Xe, the rotational spectrum of H2, and the fundamental band of H2–He. Apart from the cases of He–Ar and Ne–Ar the results of these analyses are all new.