Configuration space method to calculate rearrangement matrix elements

Abstract

Abstract A new method has been developed for calculating rearrangement matrix elements within the two-centre convergent close-coupling theory and applied to Ps formation in positron–atom collisions. The method utilises partial wave expansion of the Ps wavefunction that separates dependencies on coordinates of electron and positron. Resulting expressions contain slowly converging series which have been accelerated with use of the Euler–Wijngaarden transformation. The integrals in the method are free of the Coulomb singularity that appears in previously used momentum-space methods and therefore more straightforward to apply to complex and charged targets. The results are compared with the existing benchmark calculations for positron scattering on H and He + targets.