Self-trapped hole (STH) and self-trapped exciton (STE) states which are formed in Y3AI5Ol2, Y,SiO,, and TR,Si,O, crystals under y-irradiation in the temperature interval of 77 to 200 K are investigated. The STH is shown to be molecular 0;-, absorbing a t 1.6 eV (for Y,A1501z) and a t 1.65 eV (for Y,SiO,) and causing the eleven-component EPR signal ; the corresponding S!I' E emits a t 3.9 and 3.6 eV. In metal-doped crystals the exciton and hole delocalization lead to a decreasing of the emission energy, to a short-wave shift of the absorption band, and to the growth of the anneal temperature. At the self-localization temperature excitons are proved to migrate by jump diffusion and to transfer energy to the impurity ions exciting their emission.
The growth of LiYO2 and its structure are discussed. The absorption and luminescence spectra of Nd3+ in LiYO2 monocrystals are recorded at 4.2, 50, 77, and 300 K in the region from 250 to 2500 nm. The Nd3+ ion energy level diagram is constructed on the basis of the spectral data. Theoretical calculations of the intrinsic crystal field parameters (on the “Minsk‐22” computer) make possible to draw some conclusions about the coordination and the symmetry of the activator center. The calculated Nd3+ ion energy levels are in good agreement with the experimental ones. The colour center formation under γ‐irradiation is also investigated.
This note is a continuation of earlier published investigations of radiation stimulated effects in Y3A15012 (YAG) crystals /1, 2/. It studies the role of structure defects in recombination processes. The temperature dependence
Absorption and luminescence spectra and thermal glow curves of γ‐irradiated YAIO3 monocrystals doped with transition iron group ions are investigated. The valence states of activator ions are determined and absorption and luminescence transitions are identified. The magnitudes of the Racah parameters, B and C, and the internal crystal field strength, Dq, are calculated by means of energy matrices, which lead to the best agreement between the experimental and theoretical values of the transfer energies. The influence of ionizing radiation and high‐temperature treatments of crystals on the optic characteristics of host‐lattice and activator ions is shown.
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