Electron Spin Resonance Studies of a Reaction Intermediate in Vacuum-Sublimed NaCl and KCl

Abstract

In accordance with predictions from kinetic studies, electron spin resonance has shown that treatment of vacuum-sublimed NaCl with F2 at room temperature produces a defect containing an unpaired electron, and that the decay of this defect is retarded by Cl2. The ESR spectrum indicates an anisotropic g factor and unresolved hyperfine structure. In KCl, a spectrum is obtained which is closely similar except that the hyperfine structure is partly resolved. The spectra appear consistent with interaction of the unpaired electron with Cl atoms, rather than with F or such impurities as O or Br, and can be accounted for well by a model of the defect as linear Cl43−, i.e., an H center or something very similar. For NaCl, the spectra indicate that the vacuum-sublimed material is sometimes partly oriented. It is suggested that centers with a one-electron deficiency are observable at such high temperatures in vacuum-sublimed material because this consists of essentially perfect crystals devoid of sites which could accept a second electron from the centers.