Excitation of a hydrogen atom from its meta stable 2s to its 3s and 4s state in positron and (or) electron impact processes was investigated using Newton’s three-particle scattering equations. The effect of the second-order term was also investigated. The angle dependence of the differential cross section was studied at energies of 10 and 50 eV, respectively. Integrated cross sections are also reported in the energy region 10–200 eV. These are compared with other existing calculations.PACS No.: 36.10.Dr

A generalized form of Band's theory for rearrangement collisions based on the two state approximation in time dependent quantum-mechanical formalism is used to investigate the positron hydrogen charge exchange problem. The formalism takes into account the nonorthogonality of the rearrangement channel. The effect of nonorthogonality is to raise the cross sections from first Born results. At high energies our results approach Born results. Comparison with other calculations is also reported in the energy region 1.5 to 10 Ry.

No abstract

No abstract

The two state approximation method for the study of the rearrangement collisions is applied to the process of positronium formation in excited states for positron–hydrogen charge exchange collisions. Differential and integrated cross sections are computed for positronium formation in 2S, 2P, and 3S excited states. The results obtained in the energy region 2 to 10 Ry are compared with positronium formation cross sections in ground state. Total positronium formation cross sections including the contributions of capture into all the higher excited states of positronium are also computed in the first Born approximation and the two state approximation in the energy region considered.