Resonant X-ray Sum-Frequency-Generation Spectroscopy of K-Edges in Acetyl Fluoride.

Abstract

Resonant X-ray sum-frequency generation is calculated for excitations of the fluorine and the oxygen core K-edge in acetyl fluoride using real-time time-dependent density functional theory. The signal is generated by an extreme-ultraviolet pulse followed by an X-ray pulse with variable delay T. The X-ray pulse is tuned to different element-specific core excitations and used to probe the dynamics of a valence electronic wave packet. A two-dimensional signal is recorded depending on the dispersed X-ray pulse frequency and the frequency conjugated to T, revealing the couplings between core and valence excited states. Molecular orbital decomposition of the signal reveals which regions of the molecule contribute to the X-ray excitation.