Self-quenching of luminescence in YLF : Tm3+ crystals: I. Microscopic parameters and rates of energy transfer

Mechanisms of self-quenching of luminescence from excited H-3(4), (1)G(4), and D-1(2) multiplets of thulium ion are studied experimentally and theoret ically in YLF : Tm3+ crystals for low pump power densities. The experimenta l studies are preformed by spectroscopic methods, including the method of k inetic spectroscopy with the selective laser excitation. Microscopic parame ters and rates of energy transfer are estimated from quantum-mechanical cal culations. Spectral and kinetic properties of a concentration series of LiY 1-xTmxF4 (x = 0.001-01) crystals are experimentally studied. A comparison i s made between calculated and experimental concentration dependences of mic roscopic self-quenching rates obtained from the luminescence decay curves. It is shown that self-quenching of the H-3(4) term in YLF : Tm3+ crystals a t low concentrations (smaller than 5 at. %) can be described by the dipole- dipole interaction with the help of the hopping model. The self-quenching o f luminescence from the (1)G(4) and D-1(2) terms of thulium can be describe d by the static decay model.