Production of positronium in ground- And excited-states from positron-lithium scattering

The production of positronium during inelastic collisions of positrons with lithium atoms is a multi-channel process in which elastic scattering and positronium formation in the ground and excited-states should be considered. Thus, the problem is at least a three-channel problem. In the present work, a rather complicated computer code is developed based on the coupled-static, frozen core and Green's function partial wave expansion technique. The code is employed for treating the positron-lithium multi-channel process with the assumption that the elastic (2s channel of Li), the ground-state of positronium (or Is state) as well as the excited-state of positronium (taken as pure 2s state or as a mixture of 2s and 2p states) are open. The polarization potentials of the lithium and the excited positronium are taken into consideration. The total cross-sections, calculated with eight partial waves corresponding to the total angular momentum l = 0 to l = 7, are determined over a wide region of scattering energies ranging from 3.4 to 20 eV.