Resonant Raman scattering from excitons inTiO2

We report low-temperature resonant Raman scattering from excitons in single-crystal ${\mathrm{TiO}}_2$. From the selection rules, and from the position of the maximum of the scattering efficiency with respect to luminescence and absorption peaks, the resonance is attributed to the 2${\mathit{p}}_{\mathit{x}\mathit{y}}$ exciton. These results support the symmetry band assignment of ${\mathrm{\Gamma }}_1$ and ${\mathrm{\Gamma }}_3$ to the conduction and valence bands, respectively, and confirm that the band gap of ${\mathrm{TiO}}_2$ is direct forbidden.