Properties and reactions of uranium hexafluoride by ion cyclotron resonance spectroscopy

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.