ESR of Cl2− in various ion pairs at 4° K and the theory of V centers

Publisher Website
Google Scholar
Abstract
ESR spectra have been measured of M+Cl2 − ion pairs trapped in solid argon at 4° K, where M=Mg, Ca, Sr, Ba, Li, Na, and K. The derived g and hyperfine tensors of Cl2 − are interpreted using the simple crystal field model of Schoemaker, and the spin densities and crystal field parameters E ⊥ are compared with those for V centers in alkali halide crystals. From matrix data, it is proposed that the isotropic hyperfine coupling parameter A σ for interaction with 35Cl in pseudo‐’’free’’ Cl2 − be taken as 37±1 G. A discussion is given pointing out an approximate linear correlation between the nearest intercation distance (d) and Δg ⊥ (or A σ) among all the V K centers. Constraints imposed by lattices of varying M+/Cl− radius ratios cause variations in d and in the s/p z character in the antibonding Cl2 − electron, leading to corresponding changes in A σ and inverse changes in Δg ⊥. V F centers, with minimum constraints, have maximum values of A σ.