EPR of S2- in RbCl and RbBr

Abstract

An EPR study of a new S2- defect in RbCl is presented. A comparison with the S2- centre in RbBr, previously found by Vannotti et al. is made. For both salts a clearly resolved superhyperfine structure was observed, which has not yet been reported. The interpretation of the spectra was complicated by the simultaneous presence of the 85Rb (I=5/2) and 87Rb (I=3/2) nuclei. An excellent quantitative agreement between simulation and the experimental data was obtained, using only two parameters, i.e. the linewidth for a single superhyperfine component and the 85Rb (I=5/2) splitting. The analysis is based on the interaction of the unpaired electron on the S2- ion with four equivalent Rb nuclei. The model is consistent with an S2- ion replacing a single Cl-, respectively Br-, ion.