Time-resolved luminescence spectroscopy of LiF(U) crystals

We studied the luminescence spectra and decay kinetics of LiF(U) crystals excited by pulsed laser radiation (λ = 337 nm) in temperature range of 15–300 K. Two groups of lines with different exponential decay times are revealed in spectra. Based on comparative analysis of fast and slowly decaying luminescence spectra, temperature dependences of decay time constants, and line intensities, we conclude that electronic transitions from radiation levels of the impurity luminescence center can occur, not only in a vibrationally relaxed state, but also in a state with an excited high-frequency mode in O-U-O bonds.