Microscopic nature of Pr3+ optical centers in Y2SiO5, Lu2SiO5, and Gd2SiO5 crystals

The results of investigations of the energy spectrum, energy relaxation channels, and dynamics of electronic excitations of Pr3+ optical centers in Y2SiO5, Lu2SiO5, and Gd2SiO5 crystals are reviewed. It is shown that the crystal field of the ligands of nonequivalent cationic sites in these crystals preserves the quasisymmetry of distorted octahedra and tetrahedra; the Pr3+ activator ions are nonuniformly distributed over the nonequivalent cationic sites in Y2SiO5. For high concentrations of activator ions (>1 at.%) in Y2SiO5 crystals, the luminescence is quenched as a result of the migration and trapping of the electronic excitations energy of optical centers by traps. For Y2SiO5: Pr3+ the low-temperature mechanism of dephasing of the optical transitions of Pr3+, which is not characteristic for crystals and is due to the interaction of impurity ions with two-level systems of a multiwall adiabatic potential, is analyzed. (C) 2002 American Institute of Physics.