Color Centers in Alkali Borate Glasses Containing Cobalt, Nickel, or Copper

The absorption spectra and the magnetic moments of Co 2+ , Ni 2+ , and Cu 2+ in alkali borate glasses of various compositions and in halide‐containing glasses have been explained from the point of view of the ligand field theory. Spectra and magnetic moments are highly dependent on the composition of the base glass; this must be ascribed to the change in the coordination of the transition‐metal ions. There are far‐reaching analogies with corresponding complexes in solution or in the crystalline state.