Electronic excitation cross section in positron scattering by H₂ molecules using distorted-wave method

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 H₂ molecules by positron collisions. The integral (ICS) and differential (DCS) excitation cross sections for X¹ Σ_g⁺ → B¹ Σ_u⁺ transition of H₂ 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. (authors)