Electron excitation of the lithium 6708-Å resonance line

Abstract

We have measured the relative optical excitation function and the polarization of the 6708-Å line, using crossed beams of electrons and lithium-6, for electron energies from threshold to 1400 eV. The electron energy resolution was ∼0.25 eV, and the lithium-beam optical depth was small and varied. We have normalized our excitation function to Born theory at 1404 eV, where the energy dependence has converged to the theoretical behavior. Between 2 and 6 eV, the measured cross section is (10-45)% smaller than the results of the most recent close-coupling calculations, but the measured polarization $P$ agrees with these theories within 20% of $P$. The theoretical polarization at threshold is not observed with our energy resolution.