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排序方式: 共有399条查询结果,搜索用时 15 毫秒
391.
Light-induced scattering in photorefractive crystals 总被引:1,自引:0,他引:1
Light-induced scattering features in LiNbO3- and BaTiO3-crytals are compared with theories on holographic writing in photorefractive crystals. It is shown that they describe the experimental facts concerning the expected main scattering directions for a given incident polarization, the time development, the thickness and the wavelength dependence. Time records of the transmission offer a useful alternative for the determination of the photoconductivity. Furthermore, a new method for birefringence measurements is established. The high accuracy of this method is based on the automatic fulfillment of a phase matching condition by the anisotropically scattered radiation. 相似文献
392.
393.
The phase shifts of the extinction and refractive index gratings to the illumination pattern are revealed in doped polymethyl methacrylate (PMMA). The dynamic process of these shifts is studied via two-wave coupling at 351 nm. It is shown that these shifts are from the strain and the shrinkage inside the sample and accompanied with the photo-repolymerization process during the building process of the holographic grating. Such shifts will cause obvious energy exchange between the two recording beams and enough attention should be paid to the nonlocal property of the holographic gratings of the material in the application. 相似文献
394.
G. Mandula M. A. Ellabban R. A. Rupp M. Fally E. Hartmann L. Kovács 《辐射效应与固体损伤》2013,168(1-6):173-179
The activation energy of thermal fixing of photorefractive gratings is determined in congruent and nearly stoichiometric lithium niobate crystals, both doped with iron or manganese. The novel technique called holographic scattering method is compared with the standard two-wave mixing method. A measurement of the angular distribution of the self scattered intensity and its possible analytical function is presented. The mathematical problems of the holographic scattering method are discussed applying the angular distribution functions. 相似文献
395.
A coupled-channel model previously employed to describe the narrow Ds0*(2317) and broad D0*(2400) charmed scalar mesons is generalized so as to include all ground-state pseudoscalar-pseudoscalar and vector-vector two-meson channels. All parameters are chosen fixed at published values, except for the overall coupling constant, which is fine-tuned to reproduce the Ds0*(2317) mass. Thus, the radial excitations Ds0*(2850) and D0*(2740) are predicted, both with a width of about 50 MeV. The former state appears to correspond to the new DsJ(2860) resonance decaying to DK announced by BABAR in the course of this work. Also, the D0*(2400) resonance is roughly reproduced, though perhaps with a somewhat too low central resonance peak. 相似文献
396.
Susana Coito George Rupp Eef van Beveren 《The European Physical Journal C - Particles and Fields》2011,71(10):1762
The nature of the X(3872) enhancement is analyzed in the framework of the Resonance-Spectrum Expansion, by studying it as a regular J
PC
=1++ charmonium state, though strongly influenced and shifted by open-charm decay channels. The observed but Okubo–Zweig–Iizuka-forbidden
ρ
0
J/ψ and ωJ/ψ channels are coupled as well, but effectively smeared out by using complex ρ
0 and ω masses, in order to account for their physical widths, followed by a rigorous algebraic procedure to restore unitarity. A
very delicate interplay between the D
0
D
∗0, ρ
0
J/ψ, and ωJ/ψ channels is observed. The data clearly suggest that the X(3872) is a very narrow axial-vector c[`(c)]c\bar{c} resonance, with a pole at or slightly below the D
0
D
∗0 threshold. 相似文献
397.
Mariaconcetta Canino Gabrielle Regula Ming Xu Esidor Ntsoenzok M. Lancin Marie-France Barthe 《哲学杂志》2013,93(34):4324-4331
(111)- and (100)-oriented Si samples were implanted with Si+ ions at 1 MeV to a dose of 1?×?1016?cm?2 and with 5?×?1016 He+ cm?2 at 10?keV or 50?keV and eventually annealed in the 800–1000°C temperature range. Sample characterisation was carried out by cross-section transmission electron microscopy, positron annihilation spectroscopy and nuclear reaction analysis. In addition to the formation of He bubbles at the projected range of He, bubbles were observed after solid-phase epitaxial growth (SPEG) of the embedded amorphous Si layer. The He threshold concentration required to obtain thermally stable bubbles in amorphised Si is between one and four orders of magnitude lower than in c-Si. Since bubble formation and growth take place in the a-Si phase, the interaction with SPEG during annealing was studied by considering (100) and (111) Si. Both the SPEG velocity and the resulting defects play a role on bubble spatial distribution and size, resulting in bigger bubbles in (111) Si with respect to (100) Si. 相似文献
398.
Michael Staines Stephan Rupp Donald Pooke Steven Fleshler Ken DeMoranville Craig Christopherson 《Physica C: Superconductivity and its Applications》1998,310(1-4):163-167
Measurements of the AC loss in applied magnetic fields at 77 K have been made on model composite Bi-2223 conductors. A vibrating sample magnetometer (VSM) and a dual Hall sensor magnetometer (HSM) were used to cover the frequency range from below 0.01 Hz to over 250 Hz at AC fields up to 0.05 T rms. The VSM was limited to the frequency range below 0.2 Hz. A comparison of the two measurement techniques was possible at intermediate frequencies. The samples consisted of vertical stacks of well separated flat filaments of superconductor in Ag and Ag-alloy matrix, allowing a range of filament coupling conditions to be explored. 相似文献
399.
First experimental evidence for the existence of an electrooptic effect for cold neutrons in 7LiNbO3 is reported and discussed. The effect is based on the fact that in certain photorefractive crystals a light-induced space-charge
field can be generated which causes a modulation of the density via the inverse piezoelectric effect. From such density structures,
induced by the internal electric field, cold neutrons can be diffracted.
Received: 13 November 1998 / Revised version: 21 December 1998 / Published online: 12 April 1999 相似文献