The L x-ray spectra induced by ∼50-keV electron impact on metallic targets of uranium and thorium have been analyzed and the relative fluorescence yields of the ${\mathit{L}}_1$, ${\mathit{L}}_2$, and ${\mathit{L}}_3$ subshell of the two elements, ${\mathrm{\omega }}_2$/${\mathrm{\omega }}_3$ and ${\mathrm{\omega }}_1$/${\mathrm{\omega }}_3$, have been derived. The present values of ${\mathrm{\omega }}_2$/${\mathrm{\omega }}_3$ and ${\mathrm{\omega }}_2$ are notably different from the latest theoretical calculations and semiempirically compiled data, and also from the previous measurements using radionuclide decays to produce initial inner vacancies in the atoms. However, they are reasonable for the theoretical computation of U L x-ray relative intensities induced by a few-MeV proton bombardment on metallic uranium. The deviation is discussed and attributed mainly to an enhancement of the total relaxation effect and the shakeup process in metals with respect to those in the corresponding atomic systems as well as in the chemical compounds.

• Received 31 October 1994

DOI:https://doi.org/10.1103/PhysRevB.51.7834