Actinides: Nuclear Magnetic Resonance
Abstract
Nuclear magnetic resonance (NMR) is ubiquitously present in modern science. Offering a noninvasive microscopic probe, it has constituted an indispensable experimental tool for the study of the physics and chemistry of materials comprising a multitude of elements, from the humble hydrogen to highly complex lanthanides and actinides. In the case of the latter, however, the application of NMR has been hindered by grave difficulties predominantly arising from the very character of the atomic 5f electrons. Consequently, there have only been very few realizations of actinide nuclei NMR signal detection in solid-state compounds, and the technique has been limited in scope mostly to nuclei associated with ligand atoms. Nevertheless, recent successes in observing the NMR signal of the 235U and 239Pu nuclei have reignited the field of actinide NMR, aiming to further relevant studies and potentially the development of technological applications. In this article, after briefly introducing the basic principles of solid-state NMR, we discuss the various challenges in observing a resonance signal from actinide nuclei and how these manifest in specific isotopes. Then, we review in some detail the instances where applying NMR on the actinide nuclei directly was achieved, focusing on the recent discovery of the 239Pu signal. We conclude with an example of the value of performing NMR on ligand atoms in actinide-containing compounds to determine their ground state properties and dynamics. In particular, a summary of 17O NMR results and their interpretation in the actinide oxides family AnO2 is presented.