Elastic positronium formation and 2p-excitation cross-sections of e+ -Li scattering

Inelastic-collision processes, in which elastic, positronium formation and 2p-excitation channels are open, have been investigated for the first time within the framework of the coupled-static and frozen-core approximations. Rayleigh-Rotz variational method has been employed for calculating the binding energies and wave functions of the 1s, 2s and 2p states of the lithium atom. The partial cross-sections corresponding to 7 values of the total angular momentum l (0 ≤ l ≤ 6) are determined for 9 values of incident energy lying between 1.8 and 10 eV. Their results illustrate the stability of the iterative numerical technique employed. They demonstrate the role played by each partial wave in the total cross-sections and the importance of considering the positronium formation channel in all inelastic collisions of positrons by the atoms of alkali metals in the low-energy region. They show that the 2p-excitation channel is very important in the same energy range