Shift of the R(0) and P(1) Infrared Lines of HCl Perturbed by Noble Gases

Abstract

Adiabatic collisions, in the sense that the magnetic quantum number m is defined with respect to the rotating intermolecular axis, are shown to give a major contribution to the pressure shifts of the R(0) and P(1) lines in the vibration—rotation bands of HCl gas, perturbed by argon and by krypton. The right sign and magnitude of these shifts, however, are reproduced only if the effect of the rotation of the intermolecular axis on the rotational wavefunctions is correctly taken into account. This approximation fails in treating the shifts of the outer lines of the band, where the phase‐shift approximation of Ben‐Reuven, Friedmann, and Jaffe should apply.