A. N. Lebedenko

Interaction of Pr3+ optical centers in the Y2SiO5 crystal

It is shown on the basis of studies of the optical spectra and luminescence decay of nonequivalent Pr3+ optical centers in the Y2SiO5 crystal that the occupation of the nonequivalent cation sites of the crystal lattice by the activator ions is irregular. For excitation in the region of the optical transitions 3H4→1D2in the temperature interval 6–80 K there is no transfer of electronic excitation energy between Pr3+ ions localized in different cation sites. The luminescence decay law of the Pr3+ optical centers is determined by the concentration of activator ions and has a complicated non-single-exponential character; the quenching of the luminescence of the Pr3+ ions is due to the formation of dimers of these ions.

Peculiarities of the Ti3+ ion spectroscopy in defective corundum crystals

Abstract Basing on investigations of Al2O3:Ti3+ low-temperature optical spectra and a temperature luminescence quenching, it has been shown that the lattice defects in the form of cation and anion vacancies result in a change of the electron–phonon interaction of doped Ti3+ ions.

Manifestation of quasi-symmetry of the cation sites of Gd2SiO5, Y2SiO5, and Lu2SiO5 in the spectra of the impurity ion Pr3+

The quasi-symmetry of the inequivalent cation sites in the crystals Gd2SiO5, Y2SiO5, and Lu2SiO5 is established on the basis of an analysis of the features of the low-temperature optical spectra of the impurity ion Pr3+. One type of cation site of the crystals Y2SiO5 and Lu2SiO5 manifests the quasi-symmetry of a distorted octahedron, and the other type, that of a distorted tetrahedron. The parameters characterizing the energy spectrum of the free Pr3+ ion in the crystalline field of the cation sites are determined.

The nature of activation centers in Y2SiO5:Pr3+, Gd2SiO5:Pr3+, and Lu2SiO5:Pr3+ crystals

A complex study of the energy spectra and relaxation channels for the excitation energy of activation centers in Y2SiO5:Pr3+, Lu2SiO5:Pr3+, and Gd2SiO5:Pr3+ was performed. An analysis of the low-temperature optical spectra showed that the energy parameters and the character of field splitting of the 1D2 and 3H4 activator ion terms were substantially different in crystals of different crystallographic types. The pseudosymmetry effect was observed in splitting of the 1D2 and 3H4 terms of Pr3+ ions situated in nonequivalent crystal lattice cation sites of Y2SiO5 and Lu2SiO5. Activator ions nonuniformly populated nonequivalent cation sites of the Y2SiO5 crystal lattice. At high activator ion concentrations (>1 at %), luminescence decay in Y2SiO5 could not be described by a simple exponential time dependence. The complex luminescence decay law was caused by activator ion excitation energy migration and capture by acceptors. The role of energy acceptors was played by activator ion dimers.

Selective spectroscopy of Pr3+ impurity ions in Y2SiO5, Gd2SiO5, and Lu2SiO5 crystals

Based on a study of the low-temperature optical spectra of Pr3+ activator ions in Y2SiO5, Gd2SiO5, and Lu2SiO5 crystals, it is shown that the parameters and character of the crystal-field splitting of the 1D2 and 3H4 terms of the impurity ions are substantially different in crystals belonging to different crystallographic types. In Y2SiO5 and Lu2SiO5 crystals a pseudosymmetry effect is observed in the splitting of the 1D2 term for ions localized in inequivalent cation sites. The activator ions nonuniformly occupy the inequivalent cation sites as their concentration is increased. At high concentrations of activator ions (∼1 at. %) the optical absorption spectra exhibit spectral lines belonging to dimers of activator ions.

Features of the luminescence kinetics of Pr3+ ions in the Y2SiO5 crystal

A temperature-dependent change in the decay kinetics of the luminescence of Pr3+ impurity ions in the Y2SiO5 crystal is observed. On the basis of the deviation of the luminescence decay law from a single-exponential form and the presence of a characteristic rising front in the luminescence kinetics it is established that there is a temperature-dependent transfer of electronic excitation energy between two optical centers in the Y2SiO5 crystal.