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. 2017 Dec 27;4(6):061508. doi: 10.1063/1.4996505

FIG. 20.

FIG. 20.

(Left) Femtosecond optical pump/Ti K-edge X-ray absorption probe of bare TiO2 nanoparticles excited above the band gap. Reprinted with permission from Santomauro et al., Sci. Rep.-Uk. 5, 14834 (2015). Copyright 2015 Macmillan Publishers Ltd., licensed under CC BY 4.0. The time trace shows an ultrafast localization of the electron at a Ti atom in about 170 fs (red trace), but the large error bars imply a rise time of as long as 300 fs (grey trace). (Right) Schematic description of the electron trapping at pentacoordinated defects. The implication of the fs XAS result is that the electron is trapped at or in the immediate vicinity of the unit cell where it is created.26