PNNL

Abstract

Advanced spectroscopic techniques provide new and unique tools for unraveling the nature of the electronic structure of actinide materials. Inelastic neutron scattering experiments that address temporal aspects of lattice and magnetic fluctuations, probe electromagnetic multipole interactions and the coupling between electronic and vibrational degrees of freedom. Nuclear magnetic resonance clearly demonstrates different magnetic ground states at low temperature. Photoemission spectroscopies provide information on the occupied part of the electron density of states and have been used to investigate the momentum-resolved electronic structure and the topology of the Fermi surface in a variety of actinide compounds. Furthermore, x-ray absorption and electron energy-loss spectroscopies have been used to probe the relativistic nature, the occupation number, and the degree of localization of 5f electrons across the actinide series. More recently, element and edge-specific resonant and non-resonant inelastic x-ray scattering experiments have provided the opportunity of measuring elementary electronic excitations with higher resolution than traditional absorption techniques. Here, we will discuss the results obtained by most of these different spectroscopic techniques in studying the electronic and magnetic properties of selected actinide compounds, chosen as typical examples of systems with 5f electrons having an itinerant or a localized character, or lying near the localization-delocalization boundary.