Cross sections and annihilation rates for the elastic scattering of positrons off hydrogen and helium atoms are calculated in an approximation in which nonadiabatic distortions of the targets are treated with a model potential. The wave functions of the targets are calculated in a bicentric spheroidal coordinate system by modifying a computer code written for self-consistent-field calculations on diatomic molecules. Virtual positronium and correct long-range polarization of the targets are accounted for explicitly in the wave function by proper choice of basis functions. The wave function for each target is calculated on a grid of positron-nucleus distances, which generates a scattering potential for the positron. This is solved by applying partial-wave analysis and numerical integration. The calculated results for cross sections and annihilation rates for both systems are reasonably accurate, and suggest that the method can be extended to larger targets.

• Received 16 October 1985

DOI:https://doi.org/10.1103/PhysRevA.33.2339