Experimental and theoretical L-subshell ionization cross sections for 83Bi by electron impact from the L3 threshold to 100 keV

Abstract

We report experimental and theoretical Bi L1, L2, and L3 subshell ionization cross sections by the impact of electrons with energies from the Bi L3 ionization threshold to 100 keV. The x-ray spectra have been acquired with two Si drift detectors placed in vacuum, which allowed us to better evaluate the peak fit procedure in the L multiplet. The Lα, Lβ, Lγ, Lℓ, and Lη x-ray production cross sections, measured with relative uncertainties ranging from 5% to 9%, and two sets of atomic relaxation parameters have been used to derive the Bi L1, L2, and L3 ionization cross sections. Although the experimental uncertainties of the subshell ionization cross sections are smaller than those of the few previous measurements, they remain large due to the uncertainties associated with the relaxation parameters. Furthermore, ionization cross sections have been calculated for the three L subshells with the subconfiguration average distorted-wave (SCADW) formalism, which includes the full two-body retarded electromagnetic interaction between the projectile and target electrons. These theoretical cross sections are 15% to 30% lower than the measured values, but the agreement is reasonable given the aforementioned high uncertainties. We have also found that the simpler distorted-wave Born approximation yields subshell ionization cross sections that match those computed with the SCADW method.