An ESR study of F 32- in γ-irradiated KAsF6

An ESR study of single crystals of KAsF6, γ irradiated and observed at 77°K, has been made. A three-fluorine center similar to the Vt center, F32−, has been identified, and the principal components and directions for the g tensor, and for the fluorine hyperfine interaction tensors, have been obtained. The center is nonlinear with bond angle F–F–F = 150° ± 3°, the odd-electron density being larger on the central fluorine atom and smaller on the two equivalent end fluorine atoms of the radical. INDO calculations suggest that it is a σ-type radical with the unpaired spin density distributed in the fluorine orbitals lying in the plane of the three atoms.