Pump-Probe Resonant X-Ray Emission Spectroscopy

The pump-probe resonant X-ray emission technique has been employed to investigate the valence band spectra of graphite at the carbon K-edge. This approach enables a detailed examination of the material's electronic structure and dynamic behavior under various excitation conditions.

A comparative analysis of the pumped (red dotted curve) and unpumped (black dotted curve) resonant X-ray emission spectroscopy (RXES) spectra is conducted, focusing on a highly oriented pyrolytic graphite (HOPG) sample at the carbon K-edge (incident photon energy ħ = 295 eV). The spectra are captured at both positive (200 fs) and negative (100 fs) time delays, with the normalized intensity plotted against the photon energy loss.
The primary spectral features arise from the momentum-dependent 2p pi and sigma orbital components of the valence band within the Brillouin zone, as well as the dipolar matrix elements that couple the valence electronic states to the C 1s core-hole. A comprehensive investigation into the physical origin of the significant spectral variation observed in the pumped spectra is currently underway.