Temperature Dependence of ²³⁹Pu NMR Parameters in PuO₂

Solid-state ²³⁹Pu NMR spectra of crystalline PuO₂ have been recorded over temperatures from 11 to 295 K with better than part per thousand resolution. These experiments represent the first independent detection of ²³⁹Pu NMR in PuO₂ since the original report by Yasuoka and co-workers and extend the NMR observations to higher temperatures where recent theoretical explanations of the enigmatic magnetism and electronic structure of PuO₂ may be evaluated. The sensitivity achieved in these experiments was sufficient to measure the sinusoidal dependence of the NMR signal amplitude on the radiofrequency pulse length, which allows the determination of the nuclear g factor and magnetic moment of ²³⁹Pu. These results demonstrate the use of NMR with an open-shell f element to explore subtle magnetic effects in plutonium materials of both technological and scientific significance.