The structure of O-related luminescence centers in O-doped BaFCl was investigated by means of photoluminescence-detected electron paramagnetic resonance. It was found that one of the O-related luminescence centers was due to an excited triplet state. The fine structure parameters of this S = 1 system were D = 188mT and E = 28mT, with an angle of 17° in the ca plane between the z-axis of the D tensor and the c-axis of the crystal. The structure of the center was described as being an O-vacancy complex, where the O substituted for F with a next-nearest Cl vacancy.

Optically Detected Magnetic Resonance Investigations of Oxygen Luminescence Centers in BaFCl. S.Schweizer, U.Rogulis, K.S.Song, J.M.Spaeth: Journal of Physics – Condensed Matter, 2000, 12[28], 6237-43