Coupled-channel optical calculation for positron-lithium scattering

Abstract

Positron scattering with atomic lithium is investigated by using a coupled-channel optical method. The ionization continuum and positronium formation channels are taken into account via a complex equivalent-local optical potential. The positronium formation cross sections and the ionization cross sections, as well as the total scattering cross sections, are reported at energies above 3 eV and compared with available experimental and theoretical data.

Plasma-screening effects on positronium formation

“…Positronium (Ps) formation, which is a special rearrangement process in positron-atom collision, has been found to significantly affect the scattering process for low projectile energies in a vacuum. [21][22][23][24][25][26][27][28][29][30] As the screening effect increases in Debye plasmas, the Ps-formation threshold decreases, which results in a more important Ps process at low scattering energies. Moreover, the rate of Ps plays a decisive role in the rate of annihilation and measurement of the spectrum and distribution of the annihilation radiation can provide us with fruitful information to develop our understanding regarding the physical properties of the plasma medium.…”

Ionization cross sections for electron scattering from metastable rare-gas atoms (Ne* and Ar*)

“…This method has been used in predicting the ground-state ionization cross sections for electron scattering from various targets, [20][21][22][23][24][25][26] and the positron scattering from atoms. [27,28] The approach allows for a straightforward extension to the calculation of cross sections for ionization from metastable excited levels. [6,29] In this paper, we have used the optical potential model to calculate the electron-impact ionization cross sections for the metastable states of neon and argon, and have compared the results with experimental measurements and other theoretical calculations.…”