Emission of ThO_(2) Valence Electrons upon Excitation with Synchrotron Radiation Near the O_(4,5)(Th) Resonance Absorption Threshold

摘要

The structure of the emission spectra of ThO_(2) valence electrons, arising upon excitation with synchrotron radiation near the O_(4,5)(Th) resonance absorption threshold in the photon energy range 70 < hv < 140 eV, was examined taking into account the structure of the photoelectron spectrum and X-ray O_(4,5)(Th) absorption spectrum, and also the results of relativistic calculation of the electronic structure of ThO_(2). The line intensities in the emission spectrum of ThO_(2) valence electrons in the energy range from 0 to 40 eV considerably increases near the O_(4,5)(Th) resonance absorption thresholds at 90 and 102 eV. Appearance of this structure reflects the excitation and decay processes involving electrons of outer valence MOs (OVMOs, from 0 to 13 eV) and inner valence MOs (IVMOs, from 13 to 35 eV). These processes occur concurrently with common photoelectron emission processes. As the considered spectra at resonance are associated to a greater extent with giant Coster-Kronig transitions involving electrons of valence and inner shells, these spectra reflect the partial density of states of Th6p and Th5f electrons. The smearing of the structure in the range from approx13 to 35 eV is attributed to the IVMO formation in this oxide.