Photoionization of He above the N=2 threshold. II. Angular distribution of photoelectrons and asymmetry parameter.

Abstract

We report theoretical calculations for the ${\mathrm{\ensuremath{\beta}}}_{2\mathit{p}}$-asymmetry parameter in the photoionization of He(1${\mathit{s}}^{2}$) above the N=2 ionization threshold. We use an extension of a method recently proposed [I. S\'anchez and F. Mart\'{\i}n, Phys. Rev. A 44, 7318 (1991)] that makes use of a Feshbach partitioning of the final-state wave function and an ${\mathit{L}}^{2}$ representation of the coupled continuum states. Partial differential cross sections at emission angles 0\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{} are also provided. Our results are in good agreement with the experimental data, thus showing the accuracy of the present method to study electron angular-distribution properties.