Using X-ray free electron lasers to explore extreme states under quasi-static compression

Abstract

The exceptional brilliance of X-ray free electron lasers (XFELs) combined with quasi-static compression in diamond anvil cells (DACs) has enabled novel time-resolved methods for probing extreme states of matter. Coupling serial X-ray techniques with dynamic drivers for rapidly changing pressure and temperature, these studies offer insight into phase equilibria, chemical reaction kinetics, and geophysical processes. Here, we present the current state-of-the-art XFEL techniques used for DAC research, including serial X-ray heating, pulsed laser heating, and rapid compression. Essential questions for future investigation are also highlighted, regarding the interactions of intense X-rays with samples at high pressure and associated non-equilibrium states. X-ray free electron laser pulses can create and probe extreme states of matter at timescales, conditions, and thermodynamic pathways which are inaccessible using conventional techniques. This perspective outlines notable results and questions raised by recent experiments on pre-compressed samples, and how these can be addressed in the future.