Understanding near Fermi-level electronic structure through x-ray emission spectroscopy

Abstract

Atomic and molecular chemical properties are largely determined by the electronic structure of near Fermi-level states. Determining this structure is therefore one of the central tasks in materials characterization and development. In the work of this dissertation I explore the capabilities and limitations of non-resonant x-ray emission spectroscopy (NXES) as an analytical technique aimed at addressing these issues. To this end, I report the development of novel laboratory- and synchrotron-based instrumentation for the study of transition metal and lanthanide compounds. One of the primary results of this research thrust is increased accessibility and throughput, making NXES measurements a more viable option in routine and research-grade materials study. Using experimental data obtained from these spectrometers, I evaluate current state-of-the-art theory in terms of modeling valence structure in ambient transition-metal complexes. Additionally, I use NXES to elucidate the evolving 4f-electronic structure in the early light lanthanides under pressure. In particular these results show a persistent 4f-moment across certain volume collapse transitions in Cerium and Praseodymium, thus helping settle a long-standing debate about the nature of volume collapse.