Femtosecond M2,3-Edge Spectroscopy of Transition-Metal Oxides: Photoinduced Oxidation State Change in α‑Fe2O3

• Published in: The journal of physical chemistry letters 2013-11, Vol.4 (21), p.3667-3671
• Main Authors: Vura-Weis, Josh, Jiang, Chang-Ming, Liu, Chong, Gao, Hanwei, Lucas, J. Matthew, de Groot, Frank M. F, Yang, Peidong, Alivisatos, A. Paul, Leone, Stephen R
• Format: Article
• Language: English
• Subjects: Spectroscopy, Photochemistry, and Excited States
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz401997d

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.