Theoretical Study On The Positronium Formation In Positron-Helium,Positron-Lithium Scattering In Plasma Environments

In atomic and molecular physics,the electron-atom collisions have been highly valued,as it provides theoretical methods and experimental data support for aerospace science,plasma physics,and astrophysics.The study of positron-atom collision process is one of the fundamental issues of atomic physics,providing a novel approach to better understand the basic interactions in multi-body systems,the electronic structure inside atoms,as well as the physical mechanisms of collision process.In contrast to the interactions in electron scattering process,positron scattering has a wide range of applications in both plasma physics and material science research.Positronium(Ps)formation in positron-atom scattering is a phenomenon specific.For atoms with an ionization threshold below 6.8 e V,the Ps formation channel opens when the incident energy is 0.Recently,both theoretical and experimental physicists have been interested in the study of positron-atom scattering process.If the process can be accurately described,the fundamental kinetic components of the collision process can be extended for analysis to more complex systems.Helium atom,as the simplest multi-electron atom in the aforementioned scattering process,is the first reference object for testing the comparison of various theoretical models in positron-atom collision system.As the simplest alkali metal atom,lithium atom is of special significance for studying the positron-lithium atom interaction.Therefore,the research focus of this paper lies in the scattering process of positron-helium atom and positronlithium atom under medium energy conditions.The Debye screening potential in the plasma environment affects the interparticle interaction.Therefore,in this paper,Debye-Hückel potential is first applied to correct the potential energy term of the target atoms in Debye environment,and the corresponding potential term is approximately described by model potential,illustrating the effectiveness of the calculation of the model potential method applied in this paper compared with the existing data.On the basis of the modified potential energy term,this paper employs the equivalent local approximation method to calculate the optical potential matrix elements describing the formation of Ps,and applies the optical potential theory method to calculate the formation cross sections of positron-helium atom collision Ps(1s)and Ps(2s)and positron-ground lithium atom collision Ps under different screening factors(0 ?? ?0.25).The theoretical experimental results in this paper are compared with the research results of other researchers to demonstrate the effectiveness of the optical potential method.It can be seen that the screening effect exerts a complex influence on the formation of positronium.Additionally,the structure of helium and lithium atoms in Debye plasma environment is also presented.In the medium-energy region,with the enhancement of screening effect,the peak of Ps formation cross section of positron scattering helium atoms increases continuously and the position of maximum formation continues to move to the low energy region,and the Ps cross section of positron colliding with alkali-lithium atoms indicate a gradual decrease.