Tentative identification by ESR of a CSO 23− impurity radical in irradiated single-crystal calcite

Abstract

A paramagnetic defect tentatively identified as CSO 2 3− has been studied in irradiated natural calcite. Identification is based on chemical considerations, the fact that more than 99% of sulfur nuclei have spin zero, and upon a g value calculation which involves no adjustment of model parameters to fit the experimental data. The center is produced by room-temperature electron, γ, or X-ray irradiation but may be seen by ESR only below about 190°K. The ESR spectrum shows no hyperfine structure and consists of contributions from six inequivalent sites. Pairs of these sites are nearly equivalent and the g-tensor principal axes are nearly such that one is along a normal CO direction, a second is perpendicular to a normal Ca0Ca plane, and the third is perpendicular to the other two. The associated g values are 2.001, 2.063, and 2.008, respectively.