LAUSR

There is almost a factor of 2 increase in the full width at half maximum (FWHM) of the main Ti 2p1/2 XPS peak compared to the 2p3/2 in the closed-shell Ti(IV) compounds TiO2 and strontium titanate, STO. Although the spectra of anatase and rutile forms of TiO2 differ slightly from STO, the 2p1/2 broadening over 2p3/2 is very similar. For STO, we show that ascribing this differential broadening to a short 2p1/2 lifetime is unphysical. For STO, rigorous and fully relativistic electronic structure calculations have been carried out for both the initial state and the 2p core-hole states; these calculations include many-body effects as well as the one-body effects of spin–orbit and ligand field splittings. The agreement of the theoretical and measured XPS data for the main 2p1/2 and 2p3/2 peaks indicate that the necessary one- and many-body effects have been included. They show that the broadening is due to the presence of XPS intensity distributed over many unresolved final states for a 2p1/2 core-hole, wherea...