Quantum Theory of (H, H2) Scattering: Two-Body Potential and Elastic Scattering

Abstract

Effective two‐body interaction potentials for elastic and reactive H, H₂ scattering have been constructed from a semiempirical three‐body potential‐energy surface. Two limiting approximations were used; in one, ${\mathrm{(V}}_u^0)$ , the molecule is unperturbed by the incoming atom, and in the other, ${\mathrm{(V}}_a^0)$ , the molecule adiabatically follows the incoming atom. Since van der Waals contributions were not included in the three‐body surface, a modified two‐body potential, ${\mathrm{(V}}_m^0)$ , which included long‐range ${\mathrm{(-C\hspace{0.17em}/\hspace{0.17em}R}}^6)$ attractive terms, was also considered. Elastic differential and total cross sections were calculated for energies between 0.025 and 1.0 eV and compared with the available measurements. Although more experimental data are needed for a definitive test, the two‐body potential ${\mathrm{(V}}_m^0)$ appears to give resonably accurate results. As the coefficient $C$ is very small for H, H₂, the main effect of the van der Waals term in $V_m^0$ is to reduce the total cross section. Only small differences are found in the elastic scattering from the potentials $V_u^0$ and $V_a^0$ ; this contrasts sharply with the reactive scattering results.