Pump-probe reciprocal-space mapping using energy-resolved XFEL pink beam pulses

We present a 3D reciprocal-space mapping (RSM) method using a pink self-amplified spontaneous emission (SASE) X-ray free-electron laser beam. The energy of each specific pulse in a SASE beam can be determined using the diffraction pattern of a specimen excited by pumping itself as a spectroscopic reference. A thin slab of RSM, whose thickness corresponds to the energy bandwidth of the pink beam, is successfully reconstructed using the proposed method. By rocking a sample in a few steps, we obtained a 3D RSM covering both the diffuse scattering and the Bragg rod in NiO thin films during a pump-probe X-ray diffraction measurement.