Rovibrational excitation of molecular hydrogen in collisions with helium atoms

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Abstract
The authors have performed close-coupling calculations of cross sections for rovibrational excitation of para-H2 by He at energies extending up to 1.5 eV above the first vibrational threshold. The potential of Gordon and Secrest (1970) has been used. The n=0 to 1 vibrationally inelastic cross sections are found to differ from those of Lin (1981), who used the same potential and basis set, by factors attaining four orders of magnitude close to the n=1 excitation threshold. Structure in the variation of the vibrationally inelastic cross sections with energy, reported by Lin, is absent in the results of the authors' calculations. A comparison is made with coupled states (Alexander and McGuire, 1976) and with their own infinite-order sudden calculations. They also compare their results with measurements of the n=1 to 0 vibrational relaxation coefficient at low temperatures (Audibert et al., 1976).