We have previously calculated the cross section for radiative formation of the interesting bound state consisting of a positron bound to helium, where the atomic electrons are in the triplet spin state. That process uses the metastable triplet helium system as target, and, as expected, it has a very small cross section. In this paper we examine a more probable process in which the state of interest is produced in an exchange rearrangement collision between a positronium atom and the singlet helium ground state: $\mathrm{Ps}+\mathrm{He}\left({}^{1}S^{\mathrm{e}}\right)\to \mathrm{Ps}{\mathrm{He}}^{+}\left({}^{3}S^{\mathrm{e}}\right)+e^{-}$. The present calculation is done in the plane-wave Born approximation, using simple initial and final wave functions and compares post and prior forms.

• Received 2 August 2006

DOI:https://doi.org/10.1103/PhysRevA.75.024501