Proton–H2 scattering on an a b i n i t i o CI potential energy surface. II. Combined vibrational–rotational excitation at 4.67 and 6 eV

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Abstract
Infinite‐order‐sudden calculations have been performed at 4.67 and 6 eV on the ab initio CI potential energy surface determined recently by Schinke, Dupuis, and Lester. The vibrational degree of freedom has been treated exactly by solving vibrationally coupled radial equations. The rotationally summed differential cross sections for vibrational excitation are in good agreement with the measurements of Schmidt, Hermann, and Linder. It is shown that the rotational excitation cross sections in the vibrational ground state near the rainbow angle are almost exclusively determined by the potential between 2.5a0 and 5a0 proton–H2 separations. In this region only the V2 term of an expansion into Legendre polynomials is nonvanishing and is a factor of ∼3 smaller for the new surface than for the Giese and Gentry analytic potential. These differences result in a dramatic decrease of the rotational excitation cross sections in the rainbow region so that the present theoretical transition probabilities are in much better agreement with the experiments than our previous sudden vib–rotor calculations utilizing Giese and Gentry’s surface.