Investigation of Thorium Salts As Candidate Materials for Direct Observation of the 229mTh Nuclear Transition

Recent efforts to measure the Th-229m -> Th-229g nuclear transition sparked interest in understanding the electronic structure of wide-gap thorium salts. Such materials could be used to measure this nuclear transition using optical spectroscopy in solid-state devices. Here, we present screened hybrid density functional theory and many-body G(0)W(0) calculations of two candidate materials, namely, Na2ThF6 and ThF4, for such a measurement. Our results show an electronic gap larger than 10 eV for both materials, suggesting that the internal conversion nuclear de-excitation channel would be suppressed in these materials. We also present results for ThX4 (X = Cl, Br, I), materials with smaller gaps significantly easier to access experimentally.