Positronium Formation In Positron-Rb?positron-Cs And Positron-He Scattering

Positron collisions with atoms is one of the basic subjects in atomic and molecular physics.It provides useful information in plasma physics and astrophysics sciences.In recent years,with the emergence of strong positron beam,positron-atom collisions in plasma environment have also attracted great attention.Positronium(Ps)formation is a special physical process in positron scattering from atoms,which are different from electron scattering from atoms.The influence of positronium(Ps)formation reaction channels on the scattering process is different,in different incident energy range.When the positrons incident at high energy,the positronium(Ps)formation reaction channels have little effect for the whole scattering process,however,when the positrons incident at low and medium energy,the effect of positronium(Ps)formation reaction channels on the whole scattering process is not negligible.Therefore,positronium(Ps)formation in the collision between positron and alkali metal atoms at low and medium energy and positronium(Ps)formation in positron scattering from helium atom in plasma environments are investedgated in present work.Positronium(Ps)formation reaction channel in the collision between positron and alkali metal atoms is open at any incident energy,therefore,the relevant research work has a certain significance.We calculate the Ps(n=1)formation cross sections for positron-rubidium and positron-cesium collisions at low and medium energy in this paper,the results are compared to the available theoretical calulations,The research results demonstrates that the positronium(n=1)formation cross sections have relatively large differences at low energies,and the present results are in good agreement with the other theoretical calculations.The Debye screened potential in plasma environment has an effect on the interactions between the particles,so we have studied positronium formation in positron scattering from helium by using a modified screening approximation model in plasma environment.The Ps(1s)formation cross sections,Ps(2s)formation cross sections and total formation cross sections under for various Debye screening coefficients are given respectively.In our calculations,the Debye screened potential has a significant effect on positronium formation process,however,with the increase of incident energy,the effect gradually decreases.