Further studies of 4He–H2 vibrational relaxation

We report coupled-states cross sections for the ro–vibrational relaxation of the v=1, j=0,2,4, and 6 levels of p H2 in collision with 4He. The correlated potential surface of Raczkowski was used. For a given translational energy the total de-excitation cross sections are enhanced by initial rotation. Also, a higher degree of initial rotational excitation results in a more sharply peaked distribution of final rotational states. The qualitative energy dependence of the computed cross sections resembles that predicted by earlier three-dimensional scattering calculations. The addition of the P4(cosϑ) anisotropy into the interaction potential leads to a significant change in the vibrationally inelastic cross sections. The theoretical relaxation rates parallel the experimental values but are about five times smaller.