Properties and reactions of uranium hexafluoride by ion cyclotron resonance spectroscopy

Abstract

Ion cyclotron resonance spectroscopy has been employed to investigate the formation and reactions of both positive and negative ions derived from uranium hexafluoride. Positive ion reactions are dominated by processes whereby the various UF⁺_n fragments (n=1–3,5) react to form UF⁺₄, and by clustering of UF⁺_n (n=3–5) with UF₆. Trapped negative ion studies indicate that UF⁻₆ can be generated both by electron attachment, which is unusually slow, and by electron transfer from other species, including UF⁻₅, SF⁻₆, and Cl⁻. In addition, UF⁻₇ is observed, both in UF₆ alone, and in higher abundance when fluoride donors such as SF⁻₅ are present. Certain limits on the thermochemical properties of ions derived from UF₆ have been determined, and a high electron affinity is indicated for UF₆. The species UF⁻₆ is especially stable and much less reactive than SF⁻₆ in mixtures with acidic neutrals. The propensity of negative ions derived from UF₆ to form clusters is substantially less than observed for positive ions.