Effective twohyphen;body interaction potentials for elastic and reactive H, H2scattering have been constructed from a semiempirical threehyphen;body potentialhyphen;energy surface. Two limiting approximations were used; in one,lpar;Vu0rpar;, the molecule is unperturbed by the incoming atom, and in the other,lpar;Va0rpar;, the molecule adiabatically follows the incoming atom. Since van der Waals contributions were not included in the threehyphen;body surface, a modified twohyphen;body potential,lpar;Vm0rpar;, which included longhyphen;rangelpar;minus;Cthinsp;sol;thinsp;R6rpar;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 twohyphen;body potentiallpar;Vm0rpar;appears to give resonably accurate results. As the coefficientCis very small for H, H2, the main effect of the van der Waals term inVm0is to reduce the total cross section. Only small differences are found in the elastic scattering from the potentialsVu0andVa0; this contrasts sharply with the reactive scattering results.
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