e⁺-He scattering using an integral form of the close-coupling approximation

Abstract

An integral form of the close-coupling approximation by Ghosh and Basu (1973) and Chaudhuri at al. (1974) has been employed to investigate the processes e++He(1s2) to e++He(2s2) and e++He(1s2) to (e+e-)+He(1s). Couplings of the excited states of both the helium and positronium atoms have been neglected. Results obtained by using an approximate form of the close-coupling approximation which neglects some strong distortion effects are presented. The results in two-state close-coupling approximation do not show good agreement with the experimental findings below the positronium formation threshold. The effect of exchange of electrons is found to be appreciable in the low-energy region.