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 UFn+ fragments (n=1–3,5) react to form UF4+, and by clustering of UFn+ (n=3–5) with UF6. Trapped negative ion studies indicate that UF6- can be generated both by electron attachment, which is unusually slow, and by electron transfer from other species, including UF5-, SF6-, and Cl−. In addition, UF7- is observed, both in UF6 alone, and in higher abundance when fluoride donors such as SF5- 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 UF6- is especially stable and much less reactive than SF6- in mixtures with acidic neutrals. The propensity of negative ions derived from UF6 to form clusters is substantially less than observed for positive ions.