Electron Spin Resonance Absorption Spectrum of the AsO32− Molecule Ion in γ-Irradiated Single-Crystal Calcite

Abstract

An axially symmetric ESR absorption spectrum consisting of four principal hyperfine-structure components has been observed in γ-irradiated calcite single crystals. The symmetry axis of the spectrum is found to coincide with the crystal [111] direction, and at 77°K the spin-Hamiltonian parameters are given by g∥=2.00162, g⊥=2.00195, A∥=2627.7 Mc/sec, A⊥=2108.8 Mc/sec, eqQ=−2.4 Mc/sec, and gnβn/gβ=−0.00028. From the hyperfine structure multiplicity and the ratio of moments, it is concluded that the paramagnetic center is associated with the 100% naturally abundant 75As nucleus. This spectrum is identified as being due to the AsO32− molecule ion which occurs as a substitution for the CO32− molecule ion in calcite.