Oxygen K‐edge X‐ray absorption spectra of liquids with minimization of window contamination

• Published in: Journal of synchrotron radiation 2021-11, Vol.28 (6), p.1845-1849
• Main Authors: Vogt, Linda I., Cotelesage, Julien J. H., Titus, Charles J., Sharifi, Samin, Butterfield, Albert E., Hillman, Peter, Pickering, Ingrid J., George, Graham N., George, Simon J.
• Format: Article
• Language: English
• Subjects: Absorption spectra; Contamination; Diamonds; Modular design; NUCLEAR PHYSICS AND RADIATION PHYSICS; Oxygen; oxygen contamination; oxygen K-edge X-ray absorption spectroscopy; Sample holders; Silicon nitride; spectroscopy of liquids; Spectrum analysis; Windows (computer programs); X-ray windows
• ISSN: 1600-5775; 0909-0495; 1600-5775
• DOI: 10.1107/S1600577521009942

Oxygen K‐edge X‐ray absorption spectroscopy is used routinely to study a range of solid materials. However, liquid samples are studied less frequently at the oxygen K‐edge due to the combined challenges of high‐vacuum conditions and oxygen contamination of window materials. A modular sample holder design with a twist‐seal sample containment system that provides a simple method to encapsulate liquid samples under high‐vacuum conditions is presented. This work shows that pure silicon nitride windows have lower oxygen contamination than both diamond‐ and silicon‐rich nitride windows, that the levels of oxygen contamination are related to the age of the windows, and provides a protocol for minimizing the background oxygen contamination. Acid‐washed 100 nm‐thick silicon nitride windows were found to give good quality oxygen K‐edge data on dilute liquid samples. A high‐vacuum compatible liquid sample system for oxygen K‐edge X‐ray spectroscopy is presented, together with methods for mitigating oxygen contamination of X‐ray sample windows.