Femtosecond M-2,M-3-Edge Spectroscopy of Transition-Metal Oxides: Photoinduced Oxidation State Change in alpha-Fe2O3
Journal
Journal of Physical Chemistry Letters
Journal Volume
4
Journal Issue
21
Pages
3667-3671
Date Issued
2013
Author(s)
J. Vura-Weis
C. Liu
H. Gao
J. M. Lucas
F. M. F. de Groot
P. Yang
A. P. Alivisatos
S. R. Leone
Abstract
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-Fe 2O3 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 Fe 3+ 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. © 2013 American Chemical Society.
Type
journal article