Ionization reactions of metal hexafluorides with alkali atoms and dimers

Abstract

Ionization reactions are observed in crossed beams, usually of thermal energy, of alkalis and MoF6, WF6, and UF6. Previous studies have indicated large electron affinities for these hexafluorides, and this is confirmed here. Ionization at thermal energies proceeds with the alkali dimers A2 for the three hexafluorides, but with alkali atoms A only for UF6. Several ionization paths are observed, allowing the deduction of molecular energies. A few experiments are done with eV-range beams. Lower limits for the electron affinities are 4.5, 3.3, 4.9, 4.3, and 1.9 eV for MoF6, MoF5, WF6, UF6, and UF5, respectively. Possible mechanisms are discussed.