THE ABSENCE OF ENERGY-TRANSFER BETWEEN F-CENTER AND M-CENTER IN ALKALI-HALIDES - THE CASE OF NAF

Accurate measurements of the quantum efficiency of the M-centre lumine scence in NaF have been performed in the range of 20-300 K, by light e xcitation in the M(1) and M(F) bands; as in the KCl case, the absence of energy transfer between F and M centres after the F-centre relaxati on was ascertained. A discussion of the controversy in the literature concerning the existence of energy transfer is here presented: to reco ncile the present results with the data and speculations of different authors it is proposed that the non-radiative energy transfer, if it e xists, takes place before or during the F-centre relaxation. The absen ce of aging effects for the M-centre luminescence in NaF as well as th e absence of perturbative effects of magnesium ions in NaF:Mg have bee n verified.