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

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Abstract
The lowest partial wave is calculated for low-energy e+-H2 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 Zeff, 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.