Thomas C. Brunold, Hans U. Güdel and Enrico Cavalli
Optical spectroscopy of Ni²⁺ doped crystals of Zn₂SiO₄
Chem. Phys. Lett. 268, 413-420 (1997)                 

Abstract: The polarized 15 K absorption spectra of Zn₂SiO₄ doped with Ni²⁺ consist of three-band systems in the near-infrared (NIR) and visible (VIS) spectral regions centered at 4700, 8500, and 16500 cm^–1, respectively. In the tetrahedral approximation they are assigned to the d d transitions ³T₁ ³T₂, ³A₂, and³ T₁ (P), respectively. The spectra are interpreted in terms of a T_d C_2v site distortion and analyzed using the angular overlap model. The ligand field parameter 10Dq is 4500 cm^–1, and the Racah parameters B and C are 780 and 3630 cm^–1, respectively. By the inclusion of spin-orbit coupling in the AOM calculation it is possible to assign the rich fine structure in the origin regions of the ³T₁ ³ T₂, ³A₂ absorptions to Ni²⁺ ions occupying the two crystallographically inequivalent Zn²⁺ sites of Zn₂SiO₄.