Solution of the spin Hamiltonian with orthorhombic hf and g tensors (I = S = 1/2). II. Application to PO4−4 and Tl2+ centers in anisotropic matrices

A theory developed previously has been used in the analysis of ESR spectra of PO4−4 and T12+ in anisotropic matrices, which enables one to analyze ESR spectra characterized by spin Hamiltonian H = βH ⋅ g ⋅ S+S ⋅ A ⋅ I, where I = S = 1/2, g and A are of orthorhombic symmetry and no limitations are imposed on the relative magnitude of the hyperfine (hf) interaction. The comparison of ESR parameters for PO4−4 obtained by the newly developed treatment with those by the first‐ or second‐order high‐field approximation showed that the new theory gave better results than the high‐field approximation for the centers with a moderate hf interaction. The ESR parameters of T12+ in polycrystalline sodium metaphosphate were successfully determined from the powder pattern. This is the extreme case characterized by a dominant and anisotropic hf interaction.