Figure 2
Schematic electronic structure, the hydrogenic potential and the electron spin density.
Left panel, top: Schematics showing the excitation of electrons within shallow trap states by absorption of IR photons. Left panel, bottom: Electron spin density at self-trapped polaron Ti3+ site in bulk rutile as obtained from DFT calculations (see text). Axial and equatorial Ti-O distances are given in Angstrom. Stoichiometric bulk values are 1.951 (axial) and 1.939 (equatorial). Right panel: Hydrogenic potential at polaron Ti3+-site in bulk rutile showing the different excitations giving rise to absorption bands in the IR data. A polynomial baseline was subtracted from the raw IR data presented in Fig. 1(b) to enhance the visibility of additional hydrogenic states.
