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Femtosecond M 2,3 -Edge Spectroscopy of Transition-Metal Oxides: Photoinduced Oxidation State Change in α-Fe 2 O 3

2013; American Chemical Society; Volume: 4; Issue: 21 Linguagem: Inglês

10.1021/jz401997d

1948-7185

Josh Vura‐Weis, Chang‐Ming Jiang, Chong Liu, Hanwei Gao, J. Matthew Lucas, Frank M. F. de Groot, Peidong Yang, A. Paul Alivisatos, Stephen R. Leone,

Spectroscopy and Quantum Chemical Studies

Oxidation-state-specific dynamics at the Fe M2,3-edge are measured on the sub-100 fs time scale using tabletop high-harmonic extreme ultraviolet spectroscopy. Transient absorption spectroscopy of α-Fe2O3 thin films after 400 nm excitation reveals distinct changes in the shape and position of the 3p → valence absorption peak at ∼57 eV due to a ligand-to-metal charge transfer from O to Fe. Semiempirical ligand field multiplet calculations of the spectra of the initial Fe3+ and photoinduced Fe2+ state confirm this assignment and exclude the alternative d–d excitation. The Fe2+ state decays to a long-lived trap state in 240 fs. This work establishes the ability of time-resolved extreme ultraviolet spectroscopy to measure ultrafast charge-transfer processes in condensed-phase systems.