Fig. 4: Initial behavior of photo-generated holes near the band gap region probed by oxygen K-edge.

Experimental data of the transient signal as a function of pump-probe delay in the energy regions between VB and CB (525.8~531.2 eV) for anatase TiO2 (a) SC and (c) NC. Red: increased absorption intensity; blue: decreased absorption intensity; purple arrows: abrupt changes in transient signals by electron excitation; green arrows: traces of hole peak times from A to gap state. Red arrows: positions of center of gap states. The VBM and CBM were determined from XAS spectrum at oxygen K-edge by the linear extrapolation method. (Supplementary Fig. S2) b, d Normalized transient signals at three different photon energies (A (526.3 eV), B (530.2 eV for SC and 530.0 eV for NC), and C (531.0 eV).) during initial time delays for (b) SC and (d) NC. Experimental data (dot) agree well with calculation of our model (line). Shaded regions correspond to the standard errors.