POSITRON-HELIUM SCATTERING - RESONANCE AND DIFFERENTIAL CROSS-SECTIONS

We study positron-helium scattering using close coupling approximation (CCA) employing different combinations of the following basis functio ns: He(1s1s), He(1s2s), He(1s2p), Ps(1s), and Ps(2s), where Ps stands for the positronium atom. We observe a prominent S wave resonance of w idth 2 eV at about 30 eV, in excitation and rearrangement cross sectio ns to He(1s2s), He(1s2p), Ps(1s) and Ps(2s) states. We also report res ults of differential cross sections for the excitation of helium and p ositronium formation.