Radiation Damage of Ni 2+ ‐Doped NH 4 MgPO 4 · 6 H 2 O

An optical absorption study of NH 4 MgPO 4 · 6 H 2 O doped with Ni 2+ shows that Ni 2+ substitutes for Mg 2+ in the lattice. This spectrum is fitted to the Liehr and Ballhausen scheme for a 3d 8 ion in O h surroundings. A correlated ESR and optical absorption study of these crystals on X‐ or γ‐irradiation at room temperature indicates the formation of Ni 3+ and NH 3 + radicals. The NH 3 + center is found to have an isotropic g and A H and an anisotropic A N . This center is also produced in undoped crystals with lower yield. Ni 3+ centers are found to be paramagnetic and exhibit their characteristic optical absorption bands.