Theoretical Study On The Positron-Alkali Metal Atom Collisions And Helium Atom Structure Model Potential Method With Debye Potential

The new reaction channel that appears in the collision between positrons and atoms is the positronium formation channels.The positronium formation channels has a very important influence on the entire collision process in the low and intermediate energy region.This paper mainly applies the momentum space optical potential method in the Debye plasma environment to study the influence of the Debye potential on the structure of helium atoms and the influence of positronium formation channels of positrons scattering from alkali metal atoms on the whole collision system in the Debye plasma environment.The selected target atoms are helium atom and alkali metal atoms respectively,because helium atom is the simplest multi-electron atom,and the outermost electron of alkali metal atoms is only one electron.Their structure is simple,and calculation is easy relatively,they are ideal target atoms.We use the precise series expansion method to study the structure of helium atoms in the Debye plasma environment.Due to the screening effect of Debye plasma,when solving the wave function of helium atom,its potential energy term needs to be replaced by the model potential of the target atom,and it is described by the corrected Debye-Hückel potential.By comparing the energy levels of the ground state(1s)and excited state(2s,3s,4s,5s)obtained by the five helium atom model potentials with the experimental values,the results calculated by the helium atom model potential that are in good agreement with the experimental values,and the density distribution of the helium atom wave function under different screening factors are given.Studies have shown that the Debye plasma environment has a great influence on the structure of helium atoms.We use the momentum space optical potential method to study the collision between positrons and alkali metal atoms in the low-energy range(2 eV-60 eV)in the Debye plasma environment,and give the calculation result of the ground state(n =1)positronium formation cross sections under different screening factors.Studies have shown that in the entire incident energy range,the positronium formation channels is open,and as the incident energy increases,the positronium formation cross sections decrease rapidly,it indicates the effect of the positronium formation channel on the entire collision process,especially in the low energy range,the impact is more pronounced.It can also be concluded that the Debye potential has an influence on the positronium formation process.