Theoretical study of the low-temperature vibrational relaxation of o-H 2 in collisions with 4He

Abstract

Cross sections and rate constants for the vibrational relaxation of H 2(υ = 1, j = 1) in collisions with 4He were determined using the coupled states method with a fully-converged channel basis. The interaction potential was taken to be that of Gordon and Secrest with the elastic matrix elements modified to include the spherically-symmetric component of the semi-empirical Shafer-Gordon potential. First-order forbidden transitions play a significant role in the overall relaxation process. The cross sections for the de-excitation of the υ = 1, j = 1 level are slightly larger than those for the υ = 1, j = 0 level. The ratio of the corresponding rate constants for vibrational relaxation varies smoothly from a value of 1.25 at 500 K to 1.63 at 60 K.