Variational calculation of positron-atom scattering using configuration-interaction-type wave functions

M. W. J. Bromley, J. Mitroy
2003 Physical Review A. Atomic, Molecular, and Optical Physics  
The Kohn variational method is used with a configuration-interaction ͑CI͒-type wave function to determine the phase shifts and Z eff for positron-copper scattering. The method is first tested for positron-hydrogen scattering and it is found to give phase shifts and Z eff within 1-2% of the best previous calculations. Although the phase shift for Cu converged more slowly with L max ͑the maximum angular momentum of the electron and positron orbitals included in the short-range basis͒, it was
more » ... basis͒, it was still possible to get reliable estimates of the phase shifts by including orbitals with ᐉр18 and the use of an extrapolation technique. Calculation of Z eff was more problematic since the convergence of Z eff with respect to L max was very slow. Despite the uncertainties, it was clear that the p-wave phase shift was showing signs of forming a shape resonance at about 0.5 eV incident energy. This resulted in a p-wave contribution to Z eff that was larger than that of the s wave for kу0.1a 0 Ϫ1 . Speculative calculations based upon a model potential suggest that a p-wave shape resonance centered at thermal energies, e.g., about 0.025 eV, could result in a thermally averaged Z eff exceeding 10 000.
doi:10.1103/physreva.67.062709 fatcat:qwzvmrjhfbab7os5liea5d4yvu