Proton-impact excitation of laser-excited lithium atoms

Abstract

A time-dependent solution of the Schr\"odinger equation on a three-dimensional lattice is used to calculate proton-impact excitation cross sections for both the ground $(2s)$ and first excited $(2p)$ states of the neutral lithium atom. Total cross sections for the $2\stackrel{\ensuremath{\rightarrow}}{s}3l$ and $2\stackrel{\ensuremath{\rightarrow}}{p}3l$ excitations are compared with atomic-orbital close-coupling calculations at incident energies of 15--50 keV. In support of future experiments involving crossed ion, atom, and laser beams, total aligned cross sections for the $2p\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\sigma}}3l$ and $2p\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\pi}}3l$ excitations are presented over the same energy range. The ratio of aligned cross sections for certain excitations and incident energies is found to be almost a factor of 2.