Probabilities for2s−2pexcitation ion-atom collisions

Abstract

Expressions are derived using the semiclassical Coulomb approximation for probabilities for $2s\ensuremath{-}2p$ excitation during a collision between a target atom and a proton. Results of calculations are presented. For proton energies above 1 MeV the transition probabilities are less than \ensuremath{\sim}0.03. Unlike excitation from one atomic shell to another, our intrashell results are largely independent of the target atomic charge ${Z}_{2}$ and binding-energy difference $\ensuremath{\Delta}{E}_{2s2p}$. The shapes of our impact-parameter distributions, when scaled to the atomic radius, are similar for various targets. However, for a given target, the dependence of the $m=0$ and $m=\ifmmode\pm\else\textpm\fi{}1$ amplitudes on both impact parameter $B$ and $\ensuremath{\Delta}{E/}_{2s2p}$ is quite different, indicating that the polarization of light emitted in subsequent $2p\ensuremath{-}1s$ transitions may vary with both $B$ and $\ensuremath{\Delta}{E}_{2s2p}$. Furthermore, near $B=0$ the probabilities are sensitive to $\ensuremath{\Delta}{E}_{2s2p}$, which varies with the charge state of the target atom. Consequently, the authors suggest that dependences of collision cross sections and probabilities on the atomic charge state may be investigated by considering impact-parameter dependence or polarization fractions in $2s\ensuremath{-}2p$ atomic excitation by ion impact.