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Review date: July 24, 2003
PNNL-SA-27883

High-Pressure, Capillary X-ray Absorption Fine Structure Cell for Studies of Liquid and Supercritical Fluid Solutions

SL Wallen, DM Pfund, JL Fulton, CR Yonker, M Newville, and Y Ma. Rev. Sci. Instrum. 67(8):2843-2845 (1996).

Abstract: A method is described to acquire x-ray absorption fine structure (XAFS) spectra of high-pressure liquid and supercritical fluid solutions. The technique employs a short length of fused-silica capillary tubing that has an inner diameter of 250 µm and an outer diameter of 360 µm. A hairpin bend is formed near the center of the capillary and the bend is then placed end-on directly in the focused x-ray beam. Fluorescence spectra were acquired in a 90° geometry using a 13 element Ge detector. Demonstration XAFS spectra are reported for a Mn organometallic complex dissolved in subcritical and supercritical CO₂. Although the maximum pressure of these studies was 160 bar, with slight modification, the method will be applicable to studies requiring pressures as high as 4 kbar.