Emission decay times of F-3(+) and F-2 color centers in LiF crystals

F-3(+) and F-2 centers in LiF display efficient broad emissions in the gree n-red spectral region when excited in their absorption bands located around 450 nm. Recently it has been shown that color centers, impurities and low- dimensionality structures in heavily colored samples influence the optical cycles and in particular the lifetimes of the emitting states. In order to determine these effects we measured the decay times, which are reported in the literature with values scattered by more than a factor 4. We obtained t he radiative lifetime tau(0) = (8.1 +/- 1.2) ns for F-3(+) and tau(0) = (15 .5 +/- 0.8) ns for F-2 centers and we did not observe any temperature depen dence in the range 15-300 K. (C) 2000 Elsevier Science B.V. All rights rese rved.