We probe the dynamics of valence electrons in photoexcited [Fe(terpy)2]2+ in solution to gain deeper insight into the Fe ligand bond changes. We use hard X-ray emission spectroscopy (XES), which combines element specificity and high penetration with sensitivity to orbital structure, making it a powerful technique for molecular studies in a wide variety of environments. A picosecond-time-resolved measurement of the complete Is X-ray emission spectrum captures the transient photoinduced changes and includes the weak valence-to-core (vtc) emission lines that correspond to transitions from occupied valence orbitals to the nascent core-hole. Vtc-XES offers particular insight into the molecular orbitals directly involved in the light-driven dynamics; a change in the metal ligand orbital overlap results in an intensity reduction and a blue energy shift in agreement with our theoretical calculations and more subtle features at the highest energies reflect changes in the frontier orbital populations.
March, A. M., Assefa, T. A., Boemer, C., Bressler, C., Britz, A., Diez, M., Doumy, G., Galler, A., Harder, M., Khakhulin, D., Németh, Z., Pápai, M. I.
, Schulz, S., Southworth, S. H., Yavas, H., Young, L., Gawelda, W., & Vankó, G. (2017). Probing Transient Valence Orbital Changes with Picosecond Valence-to-Core X-ray Emission Spectroscopy
. Journal of Physical Chemistry C
(5), 2620-2626. https://doi.org/10.1021/acs.jpcc.6b12940