Ioonkristallide füüsika labor
Asukoht: W. Ostwaldi 1, Tartu
D-korpuse 2. korrus
Basic research is carried out in the field of fundamental phenomena in wide-gap materials (WGM) and their application prospects (fast scintillation detectors, selective personal dosimeters, luminescent tubes and displays, materials for nuclear energetics, etc.). The main scientific goals are to investigate in details intrinsic electronic excitations (EE) and their transformation into luminescence of different types, phonon package or Frenkel and extended defects in pure and doped binary and complex oxides and halides. The features of EE, their relaxation dynamics, bulk and surface self-trapping and recombination, energy transfer processes are studied experimentally and theoretically in single crystals, optical ceramics, thin films, nanoporous and nanosized samples.
The key feature of our experimental approach is the application of various complementary to each other spectroscopy methods using a wide energy range of exciting photons (up to 2000 eV) or electrons (1-300 keV, steady beam or single pulses) and a wide temperature range of 2−1200 K. The research group possesses several up-to-date setups for time-resolved and stationary luminescence in one- and two-photon excitation regime, cathodoluminescence, EPR, polarisation spectroscopy, and for thermoactivation spectroscopy with various detection methods. The unique setup with double VUV monochromator allows to register emissions with quantum yield down to 10-5. Radiation effects are studied in the samples irradiated by electrons, X-rays, UV-XUV photons, fast neutrons and swift ions (MeV-GeV). Synchrotron radiation (MAX-lab and HASYLAB), powerful fs-laser systems (centres in Saclay and Vilnius) and linear accelerators of swift ions (Darmstadt and Astana) are regularly used. A unique device for single crystal growth via arc-fusion method (up to 3000°C) and furnaces for the synthesis of ceramics and powders by various methods are at our disposal.
- Decay of EEs with the creation of stable lattice defects has been discovered in alkali halides and other WGM. The main mechanisms of this phenomenon under conditions of different excitation density have been revealed. [Ch.Lushchik, G.Liidya, M.Elango, A. Lushchik, T. Kärner, E. Vasil'chenko et al]
- Fundamental properties of excitons in various kinds of WGM (LiH, LiD, MgO, Al2O3, Y3Al5O12, LiLuF4, et al) have been revealed. The effect of the coexistence of free and self-trapped excitons in WGM has been experimentally discovered. [I.Kuusmann, Ch.Lushchik, V.Plekhanov, E. Feldbach, M. Kirm et al].
- Photoluminescence with a quantum yield above unity has been revealed in many WGM. The mechanisms of EE multiplication have been elucidated, the formation of secondary excitons and the direct excitation of impurity centers by hot conduction electrons have been revealed [E.Ilmas, Ch.Lushchik, A. Lushchik, M. Kirm, V. Nagirnyi et al].
- Structure of impurity luminescence centers undergoing different interaction with lattice vibrations has been clarified in WGM doped with s2-, rare-earth and other ions. Function mechanisms of spectral transformers for luminescent tubes and scintillators has been revealed. [N.Lushchik, S.Zazubovich, A.Maaroos, V.Nagirnyi, M.Kirm, S.Vielhauer et al].