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.