DIFFERENTIAL PS-FORMATION AND IMPACT-IONIZATION CROSS-SECTIONS FOR POSITRON SCATTERING ON AR AND KR ATOMS

Our previous differential cross section measurements on argon were ext ended to impact energies of 120 eV and krypton was used as an alternat ive target gas. Some distinctive features were observed in the cross s ections of the transfer and transfer-ionization reaction channel which await a theoretical explanation. The narrow feature at 45 degrees, ob served for the transfer-ionization reaction Ar(e(+), Ps e(-))Ar2+ at 7 5 eV, does not persist at 90 eV and could not be observed with krypton . Therefore, a connection to Thomas scattering (45 degrees is the Thom as angle for Ps formation) is not supported.