Positron-hydrogen scattering at low and medium energies using CCA

Abstract

The scattering of positrons by hydrogen atom has been investigated using two basis sets (a) H(1s, 2s, 2p)+Ps(1s, 2p) and (b) H(1s, 2s, 2p)+Ps(1s, 2s, 2p) in the framework of the close coupling approximation (CCA). To find the reliability and consistency of the present results test calculations with lower basis sets have also been carried out. The s-, p- and d-wave elastic phase-shifts using the above two bases are found to be variationally consistent. The authors report the elastic and excited state differential and total cross sections at medium energies For the first time using more than one capture channel in the expansion scheme. They also report the differential cross sections for the ground and excited state capture at medium energies for the first time, using coupled-state method. Present differential cross sections in the captured channels show a structure, supporting the Thomas mechanism, in ground and 2s excited state capture. The present results are found to be consistent with those of existing theoretical results except those of Hewitt et. al. (1990). The present calculation is the first systematic study that enables one to understand well the relative importance of each eigenstate in both the direct and capture channels.