Quantum calculations of rotational and NMR relaxation, depolarized Rayleigh and rotational Raman line shapes for H2(HD)−He mixtures

The two ab initio vibrotor potentials of H2−He previously published by Meyer, Hariharan, and Kutzelnigg have been composed in one potential grid. After using this potential in close coupled scattering calculations we have subsequently obtained rotational relaxation cross sections for para- and ortho-H2, NMR relaxation times for ortho-H2, depolarized Rayleigh line broadening cross sections for para-, ortho-, and normal-H2, and rotational Raman line width and shift cross sections for S0(0), S0(2) transitions, at temperatures between 20 and 450 K. The agreement with previous and more recent measurements has been found completely satisfying, with the exception of the rotational relaxation cross sections of para-H2. Throughout the paper previous results derived from the multiple property fit of Shafer and Gordon have been included for comparison. The new ab initio potential is obviously better, except for the rotational relaxation cross sections. The interaction potential of HD−He transformed from the new H2−He potential is also presented in this paper. It has been used recently in a very successful application of the Waldmann-Snider kinetic theory describing transport, relaxation, and reorientation phenomena in magnetic fields. Therefore, only the rotational relaxation cross sections, converged up to about 400 K, have been presented in this paper.