Electronic excitation cross section in positron scattering by H-2 molecules using distorted-wave method

摘要

In this work we have applied for the first time the distorted-wave approximation (DWA) combined with Schwinger Variational Iterative Method (SVIM) to describe electronic excitation of H-2 molecules by positron collisions. The integral (ICS) and differential (DCS) excitation cross sections for X-1 Sigma(+)(g) - B-1 Sigma(+)(u) transition of H-2 molecule, in the range from near threshold up to 45 eV of positron energies, were reported in static (ST) and static-correlation-polarization (STPOL) levels. Our two-state ICS in DWA-ST level have quantitative agreement with experimental measurement at energies from threshold up to 18 eV and the inclusion of polarization effects increases the cross sections. Comparison with 2-state close-coupling approximation (CCA), 2-state Schwinger Multichannel (SMC), 5-state SMC and 1013-state from Convergent Close-Coupling (CCC) methods are done and is encouraging. The relative steeper drop above 22 eV in experimental ICS was not observed by any theoretical calculations indicating that new measurements would be interesting for this transition in this energy range.