Lighting up materials with X-rays: advanced X-ray excited optical luminescence probe at the BM08-XAFS/XRF beamline, SESAME.

A highly sensitive X-ray excited optical luminescence (XEOL) probe has been developed and commissioned at the end station of the BM08-XAFS/XRF beamline, SESAME, capable of measuring emission spectra in a broad wavelength range from 200 to 950 nm with optical resolution of ∼1.60 nm, under both X-ray beam and laser (UV-Vis/NIR) excitation sources. This experimental setup is equipped with a high-sensitivity spectrometer coupled to a customized sample environment via an optical fiber of 0.22 numerical aperture. The in-house-developed sample environment contains multiple entrance windows for the simultaneous X-ray beam and laser irradiations, and an exit window to a Basler camera coupled via a focusing lens. The real-time monitoring of the emission's spatial distribution in material under element-specific X-ray excitation and laser irradiation through an integrated XEOL camera, and acquisition of the emission spectra and two-dimensional hyperspectral mapping using an integrated spectrometer, provides a powerful probe for the development of homogeneous ionizing-radiation scintillators. Such materials are critically important for advanced imaging technologies, including X-ray computed tomography. XEOL studies and hyperspectral mapping were performed on selected representative systems/X-ray scintillators including Gd3Ga5O12:Eu3+ (GGG:Eu), Gd2O2S:Tb3+, Gd2O3, semiconductor quantum dots, rare-earth ion (RE3+) complexes and organic polymer/RE3+ hybrid films to demonstrate the performance of the setup across a broad spectral range from the UV-Vis to NIR regions. The combination of XEOL with X-ray absorption spectroscopy at BM08 enables users to probe optical emission pathways in material and correlate them directly with the electronic structure and chemical environment of the photoemitting centers in the material.