The theoretical treatment of low-energy e+-H2scattering using Kohn trial functions containing Hylleraas-type functions

The lowest partial wave is calculated for low-energy e + -H 2 scattering using a Kohn trial function which includes basis functions containing the positron-electron distance as a linear factor, i.e. Hylleraas-type functions. All the necessary matrix elements are accurately evaluated using, at the most, one-dimensional numerical integration. The inclusion of Hylleraas-type functions has a very significant effect on the low-energy phaseshift; and total cross section, bringing the cross section into agreement with experiment for incident positron energies less than about 2 eV. The authors have already reported the dramatic effect the inclusion of Hylleraas-type functions has on the calculated value of Z ef f, the effective number of electrons per molecule available to the positron for annihilation. As far as they are aware, this is the first time that Hylleraas-type functions have been used in a molecular scattering calculation.