Strong geometry dependence of the X-ray Thomson Scattering Spectrum in single crystal silicon

TL;DR

This study demonstrates the strong dependence of the X-ray Thomson scattering spectrum on crystal geometry in single crystal silicon, using ultrahigh resolution measurements and benchmarking advanced TDDFT calculations.

Contribution

It introduces a complex scattering setup that reveals geometric dependencies in the XRTS spectrum and validates TDDFT predictions against high-quality experimental data.

Findings

Strong geometric dependencies observed in silicon's inelastic scattering spectrum

High-resolution data enables benchmarking of TDDFT calculations

Faster data collection demonstrated compared to previous experiments

Abstract

We report on results from an experiment at the European XFEL where we measured the x-ray Thomson scattering (XRTS) spectrum of single crystal silicon with ultrahigh resolution. Compared to similar previous experiments, we consider a more complex scattering setup, in which the scattering vector changes orientation through the crystal lattice. In doing so, we are able to observe strong geometric dependencies in the inelastic scattering spectrum of silicon at low scattering angles. Furthermore, the high quality of the experimental data allows us to benchmark state-of-the-art TDDFT calculations, and demonstrate TDDFT's ability to accurately predict these geometric dependencies. Finally, we note that this experimental data was collected at a much faster rate than another recently reported dataset using the same setup, demonstrating that ultrahigh resolution XRTS data can be collected in more general experimental scenarios.