Minima of the orientation phenomena for directs-pelectron-ion excitations in dense plasmas

Abstract

Close-encounter effects on electron-ion s\ensuremath{\rightarrow}p oriented excitations in dense plasmas are investigated using a first-order semiclassical straight-line trajectory method. Plasma-screened interaction potential is given by the classical nonspherical Debye-H\uckel model. Without using the dipole approximation, the transition probabilities and orientation parameters are obtained, for various Debye lengths and projectile energies. Including the plasma-screening effects, the transition probabilities are increased for 1s\ensuremath{\rightarrow}2${\mathit{p}}_{+1}$ transitions and decreased for 1s\ensuremath{\rightarrow}2${\mathit{p}}_{\mathrm{\ensuremath{-}}1}$ transitions. The close-encounter effects appreciably change the transition probabilities and orientation parameters for small impact parameters. It is found that the 1s\ensuremath{\rightarrow}2${\mathit{p}}_{+1}$ transition probabilities and orientation parameters have minima that correspond to the complete 1s\ensuremath{\rightarrow}2${\mathit{p}}_{\mathrm{\ensuremath{-}}1}$ transitions.