Luminescence depolarization mechanisms for color centers with the luminescence peak at 670 nm in gamma-irradiated LiF:Mg crystals

Processes of tunneling and thermal depolarization of luminescence of color centers with two absorption bands at 385 and 560 nm and the emission band peaked at 670 nm were studied in gamma-irradiated LiF:Mg crystals. As was previously concluded, relaxed excited states of the center have trigonal symmetry and are characterized by four equivalent trigonal Jahn-Teller minima corresponding to the C 3 crystallographic axes. The luminescence depolarization observed at 110–120 K results both from the thermally stimulated transition and the tunnel transition of the system between the Jahn-Teller minima. Temperature dependence of the polarization degree was calculated and compared with experimental data.