Time-Domain Ghost Imaging for Improved Laser/X-ray Pump-Probe Temporal Resolution*

We demonstrate the application of time-domain ghost imaging to improve temporal resolution in laser/x-ray pump-probe experiments conducted at free-electron lasers (FELs). In the case where a 'slow' detector, is used to record the data, the time-resolution of traditional pump-probe measurements is limited by laser/x-ray timing jitter in the detector integration window. In this context, ‘slow’ refers to detectors that are unable to readout at the full repetition rate of the FEL, and thus average over multiple FEL pulses, such is the case for large area detectors at next generation FEL facilities. We demonstrate that by correlating single-shot measurements of the laser/x-ray timing (e.g. using an x-ray/laser cross-correlator) with averaged detector values, we can reconstruct the time-dependent signal from optical-pump -- XFEL-probe measurements with temporal resolution that is no longer limited by the laser/x-ray timing jitter. Our method is especially relevant for the next generation of high repetition rate FELS. An exemplary case for time-resolved near-edge x-ray absorption spectroscopy is shown, and further applications are discussed.