Plasma-screening effects on electron-impact excitation of hydrogenic ions in dense plasmas

Abstract

Debye-H\"uckel and ion-sphere plasma screening models have been used in a study of inelastic scattering of electrons by one-electron ions in dense, high-temperature plasmas. Cross sections for transitions among the $1s$, $2s$, and $2p$ states have been calculated using close-coupling and distorted-wave descriptions. The optically allowed $1s\ensuremath{\rightarrow}2p$ and $2s\ensuremath{\rightarrow}2p$ cross sections are substantially reduced at all energies by plasma screening of the long-range dipole coupling. The $1s\ensuremath{\rightarrow}2s$ cross section is less sensitive to plasma effects. For an ion of nuclear charge $Z$, the scaled inelastic cross sections ${Z}^{4}Q$ are roughly independent of $Z$ for fixed values of $\frac{E}{{Z}^{2}}$ and $Z\ensuremath{\Lambda}$ or $Z{R}_{z}$, where $E$ is the electron's kinetic energy, $\ensuremath{\Lambda}$ is the Debye length, and ${R}_{z}$ is the ion-sphere radius.