Influence of thermoelastic stresses on self-focusing of quasicontinuous radiation

Abstract

The M4,5 photo-absorption spectra (xas) of pure CeO, and oxidised cerium have been studied. The spectrum of CeO, shows two prominent peaks in both the MS and M, regions. The stronger peaks, which occur at the energies 883.6 and 901.7 eV, are attributed to the transitions 3d'"4f1 + 3d94f2 and the other peaks which appear at the energies 888.6 and 906.5 eV are attributed to the transitions 3dl04P+ 3d94f'. Comparison of the intensity ratio Z ( f ' ) / [ I ( f I ) + I(?)] of the peaks with recent theoretical results indicates only 0.33 for the f n weight , c(,o,, in CeO,. That is, the number of 4f electrons, nf, of CeO:, is found to be 0.67 in its ground state. Measurements of the M4,5 XAS spectra of oxidised metallic cerium absorbers show that CeO, results when the metal is oxidised in air, but oxidation in oxygen results in either Ce203 or a metallic sample covered with a protective layer of Ce203. The difference between the photo-emission spectrum (XES) and the M4,5 XAS of CeOl is attributed to changes in the sample as a result of heating during the experiment.