Time-resolved pump-probe spectroscopy with spooktroscopy*

Pump-probe spectroscopy with X-ray pulses provides us with the tool to generate atomic-level movies of ultrafast processes, such as chemical bonding and charge transfer, by varying the delay between the pump and the probe pulses. Spectral domain ghost imaging, or spooktroscopy, on the other hand exploits the intrinsic variation in the X-ray pulses and enables us to probe the spectral properties with superb resolution beyond the bandwidth limit. In this work, we demonstrate a clear separation of the pump signal from the probe signal even though they are tightly overlapped in energy. Furthermore, we also show a variation of the spooktroscopy reconstruction algorithm which applies regularization on the time domain, reconstructing a time-resolved pump-probe spectroscopy measurement.