Model potential approach for positron-atom collisions. I. Positronium formation in ground state in alkali atoms Na, K, Rb and Cs using the distorted-wave approximation

Abstract

Calculations are performed within the scope of the pseudopotential formalism to predict the cross section for positronium formation during collisions of positrons with the alkali atoms Na, K, Rb and Cs employing the first Born approximation and the distorted-wave approximation. This maiden attempt allows the authors to obtain an idea of the order of magnitude of the positronium formation cross section for these atoms. Retaining both the post and the prior forms of the interaction potential in the calculation, results for the differential, total and momentum-transfer cross sections are computed at several incident positron energies in the range 0.5-20 eV.