Ultrahigh Resolution X-ray Thomson Scattering Measurements at the European XFEL

TL;DR

This paper demonstrates a novel ultrahigh resolution X-ray Thomson scattering setup at the European XFEL, enabling precise measurements of electronic features and resolving discrepancies with theoretical models, advancing research in extreme matter conditions.

Contribution

Introduction of a high-resolution XRTS method at the European XFEL that improves measurement accuracy and resolves previous experimental-theoretical discrepancies.

Findings

Accurate measurement of collective plasmon excitation in aluminium.

Resolution of discrepancies between experiments and ab initio simulations.

Potential to enhance studies of matter under extreme conditions.

Abstract

Using a novel ultrahigh resolution ($\Delta E \sim 0.1\,$eV) setup to measure electronic features in x-ray Thomson scattering (XRTS) experiments at the European XFEL in Germany, we have studied the collective plasmon excitation in aluminium at ambient conditions, which we can measure very accurately even at low momentum transfers. As a result, we can resolve previously reported discrepancies between ab initio time-dependent density functional theory simulations and experimental observations. The demonstrated capability for high-resolution XRTS measurements will be a game changer for the diagnosis of experiments with matter under extreme densities, temperatures, and pressures, and unlock the full potential of state-of-the-art x-ray free electron laser (XFEL) facilities to study planetary interior conditions, to understand inertial confinement fusion applications, and for material science and discovery.