Electron-impact excitation and ionization of atomic calcium at intermediate energies

Abstract

We present a comprehensive study of electron collisions with calcium atoms by using the convergent \emph{B}-spline \emph{R}-matrix method. Elastic, excitation, and ionization cross sections were obtained for all transitions between the lowest 39 physical states of calcium (except for $3p^6 4s5g\ ^{3,1}G$) up to the $3p^6 4s8s\ ^1S$ state, for incident electron energies ranging from threshold to 100~eV. A multi\-configuration Hartree-Fock method with non\-orthogonal term-dependent orbitals was employed to generate accurate wave functions for the target states. Close-coupling expansions including the 39 physical states plus 444 pseudo-target states of calcium were used to check the sensitivity of the results to coupling to the target continuum. The cross-section dataset obtained from the large-scale calculations is expected to be sufficiently accurate and comprehensive for most current modeling applications involving neutral calcium.