An electron paramagnetic resonance and optical absorption study was made of Ti- and V-doped material. The electron paramagnetic resonance measurements identified Ti and V in the 2+ and 3+ oxidation states; both of which were substituted for Cd. All of the centers exhibited cubic symmetry, apart from V2+, which exhibited triclinic symmetry due to strong Jahn-Teller coupling. By using photo-electron paramagnetic resonance techniques, Ti2+/Ti3+ and V2+/V3+ donor levels were determined. Internal crystal-field transitions of both ions were observed by absorption.

P.Christmann, J.Kreissl, D.M.Hofmann, B.K.Meyer, R.Schwarz, K.W.Benz: Materials Science Forum, 1995, 196-201, 779-84