Further EPR Studies of Forbidden Hyperfine Transitions ofMn2+in Calcite

A study of the forbidden hyperfine trasitions up to $\Delta m=\pm 5$ within the central fine-structure component of the EPR spectrum of ${\mathrm{Mn}}^{2+}$ in calcite is reported. The line positions are interpreted with spin-Hamiltonian parameters previously determined and with a quadrupole-interaction parameter of 0.5±0.1 G. Two approaches were used for calculating line intensities; perturbation theory and the effective-electron-magnetic field method. Good agreement with experiment was obtained.