Accurate measurements were made of the quantum efficiency of M-center luminescence, at 20 to 300K, by light excitation in the MI and MF bands. An absence of energy transfer between F and M centers, after F-center relaxation, was identified. In order to reconcile the present results with previous data and speculations, it was proposed that non-radiative energy transfer, if it existed, occurred before or during F-center relaxation. An absence of aging effects of M-center luminescence, and of perturbating effects of Mg ions in Mg-doped samples, was verified.

L.Bosi, D.Gallo, M.Zelada: Journal of Physics - Condensed Matter, 1996, 8[15], 2695-703