FIG. 3.

Oxygen K-edge XES (left) and XAS (right) spectra (markers) of CO/Ru(0001) and the corresponding fits (solid lines) measured at two selected pump-probe delays. The peak deconvolution resulting from the fit of the spectra acquired at Δt = −1 ps is shown with coloured lineshapes. The XAS data have been fitted with a Gaussian peak for the O1s→2$\tilde{\pi }$* resonance. The XES spectra have been fitted with three peaks of Voigt lineshape for the 1$\tilde{\pi }$, 5$\tilde{\sigma }$, and 4$\tilde{\sigma }$ orbitals and an asymmetric Gaussian for the d$\tilde{\pi }$ states; the elastic peak is indicated in light blue around 534 eV. The fit of the spectra at Δt = 12 ps has been performed by varying only intensity and position of the previously determined components. (Top) The positions of the fitted components measured in previous resonant gas phase experiments are also indicated.⁸⁹ (Middle) A schematic illustration of the excitation process from the O1s level to the unoccupied 2$\tilde{\pi }$* resonance in XAS and the core hole decay process from occupied molecular orbitals back to the O1s in XES. Reproduced with permission from Dell'Angela et al., Science 339, 1302 (2013). Copyright 2013 American Association for the Advancement of Science.