An electron spin resonance study of vanadium(II). Part IV. Lattice sites of dipositive ions vanadium(II) and manganese(II) in lithium and sodium fluoride crystals, and effects of X-irradiation
A numerical solution by complex Hermitian matrix diagonalisation is made for the spin eigenvalues and interpolated e.s.r. transitions for an orthorhombically sited vanadium(II) ion in lithium fluoride crystal. It is concluded that vanadium(II) ions associate with a single cation vacancy in the nearest neighbour cationic shells of lithium and sodium fluoride crystals as do manganese(II) ions in lithium fluoride crystals. Manganese(II) ions in sodium fluoride associate with cation vacancies in the next-nearest-neighbour cationic shell, and, in the presence of hydroxide anion, combine with the hydroxide anion in their first co-ordination shell. X-Rays induce vanadium(II) and manganese(II) migration by a triple process of oxidation by trapping Vk-centres (F2–), migration and then reduction back to their original oxidation state by combining with F-centres (e–). The hydroxide anion in NaF : OH– : Mn2+ inhibits this process. Thermal annealing restores the doped crystals to their original condition.