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An experimental method has been developed for determining the mechanism of luminescence of crystals by the changes arising in the intensity of a burst of their luminescence under the action of a constant electric field. An example of determining the mechanism of luminescence of AgBr crystals and AgBr0.95 and AgBr0.60Cl0.40 solid solutions by the method proposed is presented. We were the first to establish that the low-temperature photoluminescence of AgBr0.95I0.05 in the band with max = 540 nm proceeds by the Schone–Klasens recombination mechanism. It has also been established that the longwave luminescence of AgBr, AgBr0.95I0.05, and AgBr0.60Cl0.40 in the band with max = 630 nm arises as a result of the recombination of electrons localized on a luminescence center with free holes. 相似文献
956.
T. Tchen 《Journal of Russian Laser Research》2003,24(5):445-457
The Laue focusing of a spherical x-ray wave onto dynamical diffraction by a double-bent crystal system is studied. The geometrical equations of two-dimensional Laue focusing and the intensity distribution formula are derived. A high sensitivity of the two-dimensional Laue focusing to the crystal thickness and bending radii difference is revealed. It is shown that this sensitivity can be used to control the crystal thickness with accuracy up to 100 and bending radii up to 10-2 m. The focusing process of the spherical wave inside crystals as well as in vacuum is investigated. The possibility of using the two-crystal Laue system as a lens for x-ray microscopy is studied. The spectral characteristics of a twice-diffracted wave are discussed. The spectral resolution is demonstrated to be 106. 相似文献
957.
This review summarizes experience in polycrystal diffractogram analysis for 100 coordination compounds using the translation sublattice isolation technique. The most widespread cases are described, and the general strategy of analysis is proposed. Conditions for transition from a rhombohedral sublattice to cubic lattices with different centerings are discussed. 相似文献
958.
Synthesis and Crystal Structure of 18-Tungstotetranickel(II) diphosphate Na_(10){(PW_9O_(34))_2Ni_4(H_2O)_2}·26H_2O 总被引:1,自引:1,他引:0
CUI Chuan-Peng DAI Jing-Cao DU Wen-Xin WU Li-Ming FU Zhi-Yong HU Sheng-Min WU Xin-Tao② 《结构化学》2001,(4)
1 INTRODUCTIONThe inorganic chemistry concentrating on polyoxometallates, is in a position to connect elementary building blocks and their derivatives in different ways, enabling people to synthesize a large variety of remarkable substances, especially those in the "nanoworld". Of particular importance is the anionic-type which has {MOx}-type building-block units, where M stands for the d block elements in high oxidation states.[1] In 1973 Weakley, Evans and Showell isolated[2] K10P2W1… 相似文献
959.
Roman Luboradzki Janusz Lipowski Yurii A. Simonov Marina S. Fonari Edward V. Ganin Arkadii A. Yavolovskii 《Journal of inclusion phenomena and macrocyclic chemistry》2001,40(1-2):59-65
The X-ray crystal structures of two closely related molecular complexes of 15-crown-5 and benzo-15-crown-5 with 3,4-diamino-1,2,5-oxadiazole are reported (I and II). Both complexes are of 1:1 stoichiometry with the host–guest alternation in the infinitechains formed due to the unsymmetrical H-bonding patterns between the components. Crystals of I are monoclinic, P21/c, a = 7.856(3), b = 12.994(1), c = 16.033(1) , = 94.79(2)°, Z = 4, final R-factor is 0.0488. Crystals of II are orthorhombic, P212121, a = 8.260(4), b = 15.692(5),c = 13.955(7) , Z = 4, final R-factor is 0.0522. 相似文献
960.
Melting points in mixtures of a crystallizable polymer
with a low-molar-mass diluent depend on both, the diluent
fraction and the crystal thickness. A differentiation of the two
factors can be achieved by temperature-dependent SAXS
experiments. A corresponding study, complemented by DSC,
dilatometry, microscopy and AFM-imaging, was carried out for
mixtures of a poly(ethylene-co-octene) with
n-C16H34,
c-C16H32
and methyl-anthracene, respectively. All diluents lead for a
constant crystal thickness to melting point depressions in
agreement with Raoult's law. On the other hand, the effect of
the diluents on the thickness of the crystals formed at a fixed
crystallization temperature varies. While in the presence of the
two alkanes thicker crystals form, no effect arises for the
methyl-anthracene—as was previously found for the
octene-co-units. We consider these observations as a further
support for our view that polymer crystallization follows a
multi-stage route which includes a passage through an
intermediate mesomorphic phase. Under such conditions crystal
thicknesses would only be affected if the diluent is still
present in the mesomorphic phase and stay invariant if the
diluent molecules are already rejected when this intermediate
phase forms. 相似文献