Ionization of xenon L subshells by low-energy electron impact

L-subshell ionization cross sections for free xenon atoms have been measured by electron impact at incident electron energies from about one to three times the threshold energy. Ionization cross sections for the $L1$, $L2$, and $L3$ subshells were deduced from the measured yields of characteristic Lγ_2,3,4,4^', Lγ₁, and Lα1,2 x rays, using known values for the fluorescence yields wᵢ, transition probabilities Γᵢₖ, and Coster-Kronig factors fᵢₖ. The cross sections have been made absolute by normalization on the simultaneously measured bremsstrahlung intensity, using known bremsstrahlung cross sections. For the incident electron energies investigated, the subshell ionization cross sections were always larger than recently published theoretical cross sections. However, only at the lower energies is this discrepancy larger than the experimental error bars (25% to 40%).