Electron structure of excited configurations inCa2V2O7studied by electron-induced core-ionization loss spectroscopy, appearance-potential spectroscopy, and x-ray-photoelectron spectroscopy

Abstract

We have measured the electron-induced core-ionization loss (CILS) spectra, the appearance-potential (APS) spectra, and the x-ray-photoelectron (XPS) spectra of ${\mathrm{Ca}}_{2}$${\mathrm{V}}_{2}$${\mathrm{O}}_{7}$, that is a prototype for a series of luminescent materials with general formula ${M}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{7}(M=\mathrm{M}\mathrm{g},\phantom{\rule{0ex}{0ex}}\mathrm{C}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{S}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{B}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{Z}\mathrm{n},\phantom{\rule{0ex}{0ex}}\mathrm{C}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{H}\mathrm{g})$. From the analysis of the data provided by the edge spectroscopies (CILS and APS) and their comparison with the XPS binding energies, we deduced the electronic structure of the outer orbitals (occupied and empty) involved in these processes. Our data illustrate the strong many-body effects that occur in the excitation and decay of localized atomiclike configurations within the big ionic cluster ${\mathrm{V}}_{2}$${\mathrm{O}}_{7}^{4\ensuremath{-}}$. Excitation of core levels in calcium, outside the ${\mathrm{V}}_{2}$${\mathrm{O}}_{7}^{4\ensuremath{-}}$ ion, seems to involve more extended orbitals, since the screening is more efficient. Usefulness of complementary studies by x-ray emission and Auger electron spectroscopy is anticipated.