We report on atom-specific activation of CO oxidation on Ru(0001) via resonant X-ray excitation. We show that resonant 1s core-level excitation of atomically adsorbed oxygen in the co-adsorbed phase of CO and oxygen directly drives CO oxidation. We separate this direct resonant channel from indirectly driven oxidation via X-ray induced substrate heating. Based on density functional theory calculations, we identify the valence-excited state created by the Auger decay as the driving electronic state for direct CO oxidation. We utilized the fresh-slice multi-pulse mode at the Linac Coherent Light Source that provided time-overlapped and 30 fs delayed pairs of soft X-ray pulses and discuss the prospects of femtosecond X-ray pump X-ray spectroscopy probe, as well as X-ray two-pulse correlation measurements for fundamental investigations of chemical reactions via selective X-ray excitation.
S. Shreck, E. Diesen, J. LaRue, H. Ogasawara, K. Marks, D. Nordlund, M. Weston, M. Beye, F. Cavalca, F. Perakis, J. Sellberg, A. Eilert, K. H. Kim, G. Coslovich, R. Coffee, J. Krzywinski, A. Reid, S. Moeller, A. Lutman, H. Öström, L. G. M. Pettersson, and A. Nilsson, J. Chem. Phys. 347, 149, 234707 (2018).