LUMINESCENCE QUANTUM EFFICIENCY OF F-2(-) AND F-3(-) CENTERS IN LIF CRYSTALS

F-2(-) color center in LiF crystals is a unique specie of color center s concerning its photothermal stability, its broad absorption band, ce ntered at 0.96 mu m, and its broad emission band peaking at 1.12 mu m, being a tunable laser operating in the range from 1.08 mu m to 1.22 m u m. The luminescence quantum efficiency of the main transition in the laser optical cycle was determined, at room temperature, and its valu e is 0.5 +/- 0.1. This value was obtained using a method correlating t he absorption, excitation and photoacoustic spectra. Besides, the lumi nescence quantum efficiency of the fundamental transition of the F-3(- ) color center was determined. Also was estimated the energy transfer efficiency due to the overlapping of the F-3(-) center emission and th e F-2(-) center absorption bands. Possible nonradiative deexcitation m echanisms accounting for the small luminescence quantum efficiency of the F-2(-) color centers in LiF are also discussed.