A variable ultra-short-pathlength solution cell for XAFS transmission spectroscopy of light elements

An X-ray absorption fine-structure spectroscopy (XAFS) cell that is suitable for solution-phase studies of the light elements in the series from Na⁺ and Ca²⁺ is described. This cell has an ultra-short pathlength that can be remotely adjusted using a miniature stepper-motor drive and thereby readily provides transmission pathlengths in the range from submicrometer to several hundred micrometers. The flexibility to vary the pathlength enables acquisition of high-quality XAFS spectra and also allows one to check for potential distortions in the spectra from thickness effects. The primary components are mostly commercially available optical parts. The performance of this device is demonstrated at the Cl K-edge (2.8 keV) for several different aqueous Cl^- solutions.