Allowed and Forbidden Transitions in the Electron Spin Resonance of Mn2+ in CaSO4

The allowed and forbidden ESR lines of Mn 2+ in CaSO 4 have been studied. The observed hyperfine constants ( A z =-99.1 gauss, A x = A y =-99.7 gauss) indicate strong ionicity of this crystal. The expressions for the separations of the forbidden doublets in the M =±3/2↔±1/2 transitions were obtained and compared with the experimental results. The intensity of the forbidden transitions due to cross terms ( E S z S ± )(\(AS∓I±\)) was found to obey \(({sin}2)²\) rule.