Electronic excitation of H2 by positron impact: an application of the Schwinger multichannel method

In this paper we report integral and differential cross sections for positron-impact excitation of the Χ1Σg+ → Β1Σu+ transition in H2 for collision energies of 13.5, 15, 17.5, 20, 25 and 30 eV. These cross sections were derived from fixed-nuclei scattering amplitudes in such a way that low angular-momentum components are obtained using the Schwinger multichannel method and the large ones are treated by the first Born approximation. To our knowledge, no experimental data are available for comparison. Our results differ from previous theoretical results of Mukherjee and co-workers. We discuss possible reasons for this disagreement. (author)