Optical absorption and structure of impurity Ni$^{2+}$ center in   tungstate-tellurite glass
  Absorption spectra of Ni$^{2+}$ ions in 22WO$_3$--78TeO$_2$ tungstate-tellurite glass were studied and Ni$^{2+}$ extinction coefficient spectral dependence was derived in the 450 -- 2700 nm wavelength range. Computer modeling of the glass structure proved Ni$^{2+}$ ions to be in trigonal-distorted octahedral environment in the tungstate-tellurite glass. Tanabe-Sugano diagram for such an environment was calculated and good description of the observed spectrum of Ni$^{2+}$ ion was obtained. Basing on both absorption spectral range width and the extinction coefficient, nickel should be considered among the most strongly absorbing impurities in the tellurite glasses. 
V.G.Plotnichenko, V.O.Sokolov, G.E.Snopatin, M.F.Churbanov
cond-mat.mtrl-sci physics.optics