Electron-impact excitation of Li to high principal quantum numbers

Abstract

The time-dependent close-coupling method is used to calculate electron-impact excitation cross sections for the [Formula Presented] and [Formula Presented] transitions at incident energies just above the ionization threshold. The implementation of the time-dependent close-coupling method on a nonuniform lattice allows the study of continuum-coupling effects in excitations to high principal quantum number, i.e., [Formula Presented] Good agreement is found with R-matrix with pseudostates calculations, which also include continuum-coupling effects, for excitations to low principal quantum number, i.e., [Formula Presented] Poor agreement is found with standard distorted-wave calculations for excitations to all principal quantum numbers, with differences still at the 50% level for [Formula Presented] We are able to give guidance as to the accuracy expected in the [Formula Presented] extrapolation of nonperturbative close-coupling calculations of low n cross sections and rate coefficients. © 2003 The American Physical Society.