L-subshell-ionization cross sections of tungsten by electron impact near the threshold region.

Abstract

L-subshell-ionization cross sections ${\ensuremath{\sigma}}_{3}$/${\ensuremath{\sigma}}_{2}$ and ${\ensuremath{\sigma}}_{2}$/${\ensuremath{\sigma}}_{1}$ for ${L}_{3}$, ${L}_{2}$, and ${L}_{1}$ levels for tungsten have been measured by electron impact at incident electron energies from about one to three times the ionization threshold energy of the ${L}_{1}$ subshell. Ionization cross sections for the ${L}_{1}$, ${L}_{2}$, and ${L}_{3}$ levels were deduced from the measured intensity radiations L${\ensuremath{\beta}}_{3}$, L${\ensuremath{\beta}}_{1}$, and L${\ensuremath{\beta}}_{2}$ and using known values for the fluorescence yields, radiative transition probabilities, and Coster-Kronig parameters. The x-ray spectra were obtained with a curved crystal spectrometer (50 cm radius) and recorded on photographic film. Comparison is made with experimental measurements of Chu-Nan Chang and theoretical calculations of Gryzinski and McGuire. A good agreement is achieved for electron-beam energies ${E}_{0}$\ensuremath{\ge}1.25 times the energy ${E}_{1}$ of ${L}_{1}$-level ionization.