Spectroscopic Properties of Ni²⁺Ions in Octahedral Complexes

Based on an up-do-date literature data， we consider an empirical trend between the energy of the spin-forbidden ³A₂-¹E transition of the octahedrally coordinated Ni²⁺ ions and a new nephelauxetic parameter β 1 = B / B 0 2 + C / C 0 2 （B， C （B₀， C₀） are the Racah parameters of Ni²⁺ ions in a crystal（free state）， respectively）. It is demonstrated that the energy of the Ni^{2+ 1}E state is a linear function of the β 1 parameter. These findings prove importance of a simultaneous consideration of reduction of both Racah parameters B and C due to the nephelauxetic effect. Such an approach is more accurate in estimating the energy position of the ¹E level. The commonly used nephelauxetic ratio β = B / B 0 ， which completely ignores the reduction in the values of the Racah parameter C， is not accurate enough for this purpose. The collected in the present paper experimental data and their analysis can be useful for researchers working with the crystalline materials doped with Ni²⁺ ions.