X-ray TiKspectra and band structures of oxides of titanium

The Ti $K$ emission and absorption spectra of the titanium oxides $\mathrm{Ti}{\mathrm{O}}_x$ ($x=0, 0.4, 0.84, 0.9, 1.0, 1.12, 1.25, \mathrm{and} 2$) have been measured with a two-crystal spectrometer by means of a step scanning method. The emission spectra were obtained by the fluorescent excitation method. Results are compared with the calculated density of states proposed till now with emphasis on the effect of the oxygen concentration on the electronic structure. The calculated density of states of $\mathrm{Ti}{\mathrm{O}}_x$($x=0.80, 0.91, 1.0, 1.08, \mathrm{and} 1.22$) crystallizing in the rocksalt structure explains qualitatively the observed profiles of the $K$ spectra of these substances, both the emission and absorption spectra. However, in detail there exist several discrepancies between the experimental results and the calculation with respect to the forbidden energy gap and the detailed structure of the oxygen $2p$ band and so on. The molecular-orbital theory provides a suitable interpretation for the $K$ spectra of the nonmetallic compound Ti${\mathrm{O}}_2$.