THRESHOLD BEHAVIOR OF VIBRATIONALLY INELASTIC CROSS-SECTIONS

Converged cross sections for the vibrational processes (0, j)→(l, j′) for the system para-H2 + He are presented at eleven energy values below 1 eV. Pronounced structures in these cross sections, similar to those first observed by McGuire and Toennies but not detected in some other calculations, are studied in detail. It is shown that the rotational coupling and energy gap between the initial and/or final state of a transition and the state just opening up play important roles in the threshold behavior of the cross sections. © 1979 American Institute of Physics.