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

We report theoretical calculations for the β₂ₚ-asymmetry parameter in the photoionization of He(1s²) above the N=2 ionization threshold. We use an extension of a method recently proposed [I. S\'anchez and F. Mart\'{}n, Phys. Rev. A 44, 7318 (1991)] that makes use of a Feshbach partitioning of the final-state wave function and an L² representation of the coupled continuum states. Partial differential cross sections at emission angles 0^∘{} and 90^∘{} 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.