Screening effects in the ionization of molecules by positrons

Theoretical DWBA calculations for the ionization of N2, CO, CO2 and CH4 molecules are presented. Previous calculations are improved by calculating the wavefunctions of the ejected electron and of the positron in the spherically averaged, screened field of the molecule. Results for N2 and CO are in very good agreement with the experimental data, while those for CO2 and CH4 need more improvement.