Electron-electron Thomas peak in fast transfer ionization

Abstract

``Thomas process'' is a name used for a family of singular two-step processes that can lead to electron transfer. The Thomas process of the ``second kind,'' occurring in reactions with both transfer and ionization, utilizes the $e\ensuremath{-}e$ scattering in the second step, so this Thomas process requires the dynamics of the electron-electron interaction. We calculate numerically the second order element of an S matrix and corresponding cross sections for the transfer ionization process. We find that the position and shape of the Thomas peak depend on both electron-electron and the electron-nucleus interaction. Also the direct and exchange amplitudes are equal at the peak position. We test the peaking approximation used for transfer ionization. Our results can be compared to experimental results for ${p}^{+}+\mathrm{He}\ensuremath{\rightarrow}{\mathrm{H}+\mathrm{H}\mathrm{e}}^{2+}{+e}^{\ensuremath{-}}.$