High-resolution absorption measurements with free-electron lasers using ghost spectroscopy

TL;DR

This paper introduces a robust ghost spectroscopy method for high-resolution x-ray and EUV absorption measurements at free-electron laser sources, enabling faster and more precise spectral analysis of materials.

Contribution

The study presents a novel ghost spectroscopy technique that achieves higher resolution and shorter measurement times than traditional narrow-band scanning methods at free-electron lasers.

Findings

Ghost spectroscopy reconstructs spectral response with high resolution.

Measurement time is shorter than narrow-band scanning under certain conditions.

Method is effective for materials like silicon and silicon compounds.

Abstract

We demonstrate a simple and robust high-resolution ghost spectroscopy approach for x-ray and extreme ultraviolet absorption spectroscopy at free-electron laser sources. Our approach requires an on-line spectrometer before the sample and a downstream bucket detector. We use this method to measure the absorption spectrum of silicon, silicon carbide and silicon nitride membranes in the vicinity of the silicon L2,3-edge. We show that ghost spectroscopy allows the high-resolution reconstruction of the sample spectral response using a coarse energy scan with self-amplified spontaneous emission radiation. For the conditions of our experiment the energy resolution of the ghost-spectroscopy reconstruction is higher than the energy resolution reached by scanning the energy range by narrow spectral bandwidth radiation produced by the seeded free-electron laser. When we set the photon energy resolution of the ghost spectroscopy to be equal to the resolution of the measurement with the seeded radiation, the measurement time with the ghost spectroscopy method is shorter than scanning the photon energy with seeded radiation. The exact conditions for which ghost spectroscopy can provide higher resolution at shorter times than measurement with narrow band scans depend on the details of the measurements and on the properties of the samples and should be addressed in future studies.