LCLS in - photon out: fluorescence measurement of neon using soft x-rays

TL;DR

This study measures neon's fluorescence yield under soft x-ray irradiation using LCLS, demonstrating a novel spectrometer setup and estimating beam focus size through theoretical modeling of ionization processes.

Contribution

It introduces a grazing incidence spectrometer for gas phase x-ray fluorescence spectroscopy and provides a theoretical framework to estimate beam focus size from fluorescence data.

Findings

Neon fluorescence yield measured at ~1200 eV

Successful implementation of a variable linespacing grating spectrometer

Estimated beam focal size using theoretical ionization models

Abstract

We measured the fluorescence photon yield of neon upon soft x-ray ionization (~1200 eV) from the x-ray free electron laser at Linac Coherent Light Source, and demonstrated the usage of a grazing incidence spectrometer with a variable linespacing grating to perform x-ray fluorescence spectroscopy on a gas phase system. Our measurements also allowed us to estimate the focal size of the beam from the theoretical description developed, in terms of the rate equation approximation accounting for photoionization shake-off of neutral neon and double Auger decay of single core holes.