Improved Instrumentation and Application of X-ray Emission Spectroscopy

Abstract

Since its discovery x-ray fluorescence has been used to understand atomic scale phenomenon. With technological and scientific improvements x-ray fluorescence spectroscopy has become a widespread analytical technique for elemental identification and led to the development of high-resolution x-ray fluorescence spectroscopy, or x-ray emission spectroscopy (XES) which allows for an elemental selective probe of local electronic structure and ligand environment, expanding the analytical and scientific uses x-ray fluorescence. Here, I explore the applications of XES and present development of XES technique and spectrometers to further the analytical and scientific capabilities of XES. First, I present a study of cementitious materials for use in storage of nuclear waste. I show that XES is an accurate method to calculate reduction capacity through sulfur speciation and develop a new instrumental technique to improve study of small samples with XES. I incorporated this technique into a new laboratory instrument designed for high throughput analytical study of air-sensitive phosphorus samples and show the time dependent oxidation of NiP nanoparticles. Second, I examine asymmetric Rowland circle geometry for modern use in laboratory and synchrotron facilities. I collaborated on developing a new spectrometer with this capability which demonstrated the improved resolution and flexibility asymmetric geometries provide. I then present a tool designed for selection of these asymmetric geometries. Finally, I study the directionality of electronic and ligand structure of asymmetric single crystals. X-ray emission spectropolarimetry was shown to select for fluorescence from specific dipole transitions which contain information about the orbitals involved and a new technique is presented that obtains the same information by careful analysis of standard XES spectra.