[en] Persistent photoinduced changes of optical absorption have been found in garnet Ca₃Ga₂Ge₃O₁₂ doped with manganese. Irradiation by a He--Ne laser of 633 nm wavelength results in a noticeable increase in the absorption coefficient of the crystal. The photoinduced changes are observed up to room temperature as distinct from concentrated manganese garnets in which the photoinduced absorption vanishes at much lower temperatures. The wide temperature range of the existence of the photoinduced effect together with a high transparency of the crystal makes it a promising material for optical recording. Copyright 2001 American Institute of Physics

[en] The ^archPbMoO₄ scintillating crystal has been produced from archaeological lead for the first time. The advanced technique for deep purification of lead against chemical impurities was used resulting in 99.9995% purity level of final material. The ^archPbMoO₄ crystal was characterized by means of cryogenics bolometric measurements and demonstrates excellent performances as a scintillating bolometer. The energy resolution (0.3% at 1462 keV of ⁴⁰K), the high light yield (5.2 keV/MeV for γs, and 1.2 keV/MeV for α particles) and the highly efficient particle identification achieved with this detector, representing the high quality of the crystal. As a final proof for the feasibility of the ^archPbMoO₄ crystal as a promising detector to search for the neutrinoless double β-decay of ¹⁰⁰Mo, the crystal should be produced using the LTG Czochralski technique to prevent the possible contamination during the crystal growth and to increase the production yield. (paper)

[en] The lasing efficiency of Nd³⁺ ions is studied in laser materials capable of self-Raman frequency conversion. The lasing properties of tungstate and molybdate crystals with the scheelite structure (SrWO₄, BaWO₄, PbWO₄, SrMoO₄, PbMoO₄) activated with neodymium ions are investigated upon longitudinal pumping by a 750-nm alexandrite laser or a 800-nm diode laser. The slope lasing efficiency obtained for a Nd³⁺:PbMoO₄ laser emitting at 1054 nm is 54.3% for the total lasing efficiency of 46%, which is the best result for all the crystals with the scheelite structure studied so far. The simultaneous Q-switched lasing and self-Raman frequency conversion were demonstrated in neodymium-doped SrWO₄, PbWO₄, and BaWO₄ crystals. (papers devoted to the 90th anniversary of a.m.prokhorov)

[en] The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y₃Al₅O₁₂, YAG) and yttrium oxide (Y₂O₃) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced reactivity, which significantly decreases the temperature range of interaction in the Y₂O₃-Al₂O₃ system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation of the YAG crystal structure from cubic to tetragonal.

[en] The comparative study of the multi-wave stimulated Raman scattering (SRS) oscillation in PbMoO₄ and PbMo_0.5W_0.5O₄ crystals under 18-ps laser pumping at the wavelength of 1064 nm is carried out. It is shown that because of four-wave mixing of the Raman radiation components in the crystals with a short length (∼ 1 cm) the oscillation thresholds of the 2nd (at the wavelength of 1306 nm) and the 3rd (at the wavelength of 1473 nm) Stokes radiation components are significantly reduced relative to the values defined by the cascade mechanism of stimulated Raman scattering. At the same time in the PbMo_0.5W_0.5O₄ composite crystal the multi-Stokes SRS oscillations were observed containing different combinations of the Raman frequency shifts corresponding to a structure of the plumbic molybdate and tungstate. At the 1st Stokes radiation component, splitting to the wavelengths of 1173 and 1178 nm, the Raman shifts of 869 cm^-1 (plumbic molybdate structure) and 904 cm^-1 (plumbic tungstate structure) were observed. At the 2nd Stokes radiation component, splitting to three wavelengths of 1306, 1312, and 1318 nm the frequency shifts of 2×869 cm^-1, (869 + 904) cm^-1, and 2×904 cm^-1, respectively, from the pumping wave were observed

[en] PbF₂-and BaF₂-doped PbWO₄ crystals have been grown by the Czochralski method. The scintillation characteristics of the grown crystals have been determined. It is shown that introduction of BaF₂ leads to an increase in the light yield of PbWO₄ crystals by 20%, while PbWO₄:PbF₂ crystals demonstrate a significant increase in radiation hardness.

[en] We report on the first compelling observation of α decay of ¹⁵¹Eu to the ground state of ¹⁴⁷Pm. The measurement was performed using a 6.15 g Li₆Eu(BO₃)₃ crystal operated as a scintillating bolometer. The Q-value and half-life measured are: Q = 1948.9±6.9(stat.) ± 5.1(syst.) keV, and T_1/2 = (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 10¹⁸ y. The half-life prediction of nuclear theory using the Coulomb and proximity potential model are in good agreement with this experimental result. (paper)

[en] Long-lived photoinduced absorption and dichroism in the Ca₃Ga_2-xMn_xGe₃O₁₂ garnets with x < 0.06 were examined versus temperature and pumping intensity. Unusual features of the kinetics of photoinduced phenomena are indicative of the underlying electronic processes. The comparison with the case of Ca₃Mn₂Ge₃O₁₂, explored earlier by the authors, permits one to finally establish the main common mechanisms of photoinduced absorption and dichroism caused by random electric fields of photoproduced charges (hole polarons). The rate of their diffusion and relaxation through recombination is strongly influenced by the same fields, whose large statistical straggling is responsible for a broad continuous set of relaxation components (observed in the relaxation time range from 1 to about 1000 min). For Ca₃Ga_2-xMn_xGe₃O₁₂, the time and temperature dependences of photoinduced absorption and dichroism bear a strong imprint of structure imperfection increasing with x