Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas

Abstract

Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas have been investigated by employing the exterior complex scaling method. The interactions between charged particles in the plasmas have been represented by Debye-H\"uckel potentials. The $1s\ensuremath{-}1s$ elastic collision strengths below the $n=2$ excitation threshold of ${\mathrm{He}}^{+}$ dominated by resonance structures are calculated for different screening lengths. As the screening strength increases, the resonance peaks studied ${[}_{2}{{(1,0)}_{2}}^{+}{}^{1}{S}^{e},{}^{3}{P}^{o},{}^{1}{D}^{e}$, and ${}_{2}{{(0,1)}_{2}}^{+}{}^{1}{P}^{o}]$ exhibit blueshifts and then redshifts with a further increase of the screening strength, which results in dramatic changes of the collision strengths. It is found that these dynamic variation features of the resonances are related to the changes of energy levels of ${\mathrm{He}}^{+}$ in the screened potential and geometric configurations of resonances. Triple-differential-ionization cross sections in coplanar geometries at 6-Ry incident electron energy are also reported, significant changes are observed with varying screening length.