ELECTRON SPIN RESONANCE ABSORPTION SPECTRUM OF ASO22- MOLECULE-ION IN GAMMA-IRRADIATED SINGLE-CRYSTAL CALCITE

An electron spin resonance absorption spectrum corresponding to S = 1/2, I = 3/2, and exhibiting orthorhombic symmetry has been observed in γ-irradiated single-crystal calcite. At 4.2°K, the spin-Hamiltonian parameters are gzz= 2.0150, gxx= 1.9991, gyy= 1.9910, Azz= -152 MHz, Axx= 614 MHz, Ayy= -173 MHz, (gnβn/h) = -7.24×10-4 MHz/Oe, e2gQ=16.2 MHz, and η≅0. The paramagnetic defect associated with this spectrum is identified as the AsO22- molecule-ion which is located at carbonate ion sites with its plane coincident with that of the carbonate ions. From the hyperfinhe structure splittings and the g-tensor anisotropy, it is deduced that the unpaired electron has approximately 1% 4s, 96% 4p, and 3% 4d character and that it is almost completely localized on the arsenic atom.