Enhanced ultrafast X-ray diffraction by transient resonances

Ionization and the resulting sample bleaching is regarded as detrimental for X-ray imaging. The X-ray scattering signal generally decreases as electrons are removed from the parent ion, a process which ultimately limits the quality of X-ray images. However, in this study we find that ionization can create short-lived electronic states which are beneficial for imaging and increase the scattering cross section compared to the neutral atom. We compared snapshots from individual 100 nm Xe nanoparticles as a function of the X-ray pulse duration and incoming X-ray intensity in the vicinity of the Xe M-shell resonance. Surprisingly, images recorded with few femtosecond and sub-femtosecond pulses are up to 10 times brighter than the static linear model predicts. Our Monte-Carlo simulation and statistical analysis of the entire data set confirms these findings and attributes the effect to transient resonances. Our simulations suggest that the scattering cross section may increase by several orders of magnitude when targeting specific resonances. Our study guides the way towards CDI with unprecedented combination of spatial and temporal resolution at the nanoscale.