Samples of Ti-doped sapphire exhibited a 420nm blue emission band whose corresponding excitation band lay at 244nm. Synchrotron radiation measurements were made of the vacuum ultra-violet to ultra-violet absorption spectrum, and the results suggested that the blue emission was due to a center other than a trivalent Ti3+ ion or a tetravalent Ti4+ ion. A more probable candidate was proposed to be an F+-type color center.

W.Chen, H.Tang, C.Shi, J.Deng, J.Shi, Y.Zhou, S.Xia, Y.Wang, S.Yin: Applied Physics Letters, 1995, 67[3], 317-9