Vibrational relaxation in the para-H₂-⁴He system: Comparison of coupled-channel, coupled-states, and effective potential methods

Abstract

Coupled-channel scattering calculations are performed in the energy range of 0.9 to 2.0 eV using both the Gordon-Secrest and the extended Tsapline-Kutzelnigg potentials. Vibrational relaxation rates for p-H 2-4He are computed over the temperature range 50 to 2000°K. Cross sections and relaxation rates are compared to results of coupled-states and effective potential calculations. We find quantitative agreement with coupled-states results and order-of-magnitude agreement with effective potential results. At high temperatures (around 1000 °K), relaxation rates computed using coupled-channel cross sections with both the extended TK and GS potentials agree well with experiment. At low temperatures (50 to 500 °K), the present CC-GS results lie a factor of 4 above the experimental data, while the CC-TK results are at least a factor of 10 below experiment. © 1978 American Institute of Physics.