Progress with the Schwinger multichannel method in positron–molecule scattering

Abstract

We report calculations for low-energy positron–C 2H 2 and –N 2 scattering obtained through the Schwinger multichannel method (SMC). Integral and differential cross-sections and the annihilation parameter, Z eff, are presented. For nitrogen, evidence of a Ramsauer–Townsend minimum and the possibility of overcorrelation in the scattering configuration space are discussed. Annihilation probability densities (APD) calculated for He and H 2 seem to bring indirect support to a model previously proposed to explain why acetylene, unlike nitrogen, presents very high low-energy annihilation rates.