Investigation of warm dense matter using time-resolved X-ray absorption spectroscopy with third- and fourth- generation light sources

The advent of high-power lasers has provided insights into laboratory high energy density (>1011 J/m3) physics. In particular, the properties of warm dense matter (WDM) with temperatures of 104–106 K and near-solid densities is a research area that has garnered significant interest recently. However, owing to the high temperatures and pressures associated with WDM, the measurement of fundamental properties is difficult, and insufficient data has been a significant setback in WDM research. Herein, we review recent developments in time-resolved X-ray absorption spectroscopy with synchrotron and X-ray free electron lasers for WDM research. Various physical properties, such as atomic bonding, electronic structures, electron–phonon coupling, and thermal conductivity of various elements in WDM conditions are investigated via this noble X-ray technique at various time scales from 100 ps to 100 fs. [Display omitted] •WDM is an intermediate state between condense matter and plasma, which has complicated interplay of physical processes.•Typical TR-XAS technique based on 3rd and 4th generation light source combined with high-power laser system is reviewed.•Various physical properties of several elemetns in WDM conditions investigated with TR-XAS are reviewed.•Novel approaches to measure ultrafast nonequilibrium dynamics with normalization of single XFEL pulse are introduced.