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Hu H.-C.,China Institute of Atomic Energy
Acta Crystallographica Section A: Foundations of Crystallography

During the preparation of versatile tables for the secondary extinction factor Yμ of cylindrical and spherical mosaic crystals expressed as functions of the Bragg angle θ, absorption coefficient times radius μ θ and reduced radius τ0 = σ0ρ [σ0 = (2π)1/2Q/η], or of θ, τ0 and ξ0 = μ/σ0, five kinds of Students Tn probability functions T1, T2, T3, T4, T∞ for describing the mosaic distribution of crystals have been tested. T1 is Lorentzian (L) and T∞ is close to Gaussian (G). The influence of these different mosaic distributions upon the reflection power ratio, the integrated reflection power ratio (the area under the rocking curve) and the extinction factor Y μ in cylindrical crystals has been thoroughly investigated. For a weakly absorbing cylindrical crystal with τ0 = 30, the value of Yμ for the T2 distribution turns out to be nearly two times the value for G, but the difference between these distributions becomes small when ξ 0 > 1. The L distribution has been found to be unsuitable for describing the mosaic distribution. The determination of different types of mosaic distribution from the rocking curves is discussed based on these results. Finally T2, T4 and the G distribution have been found to be acceptable for the calculation of secondary extinction factor tables for cylindrical and spherical crystals. © 2010 International Union of Crystallography Printed in Singapore - all rights reserved. Source

Dong J.,CAS Lanzhou Institute of Modern Physics | Zuo W.,CAS Lanzhou Institute of Modern Physics | Gu J.,China Institute of Atomic Energy
Physical Review C - Nuclear Physics

Based on the Skyrme energy density functional, the spatial distribution of the symmetry energy of a finite nucleus is derived in order to examine whether the symmetry energy of a finite nucleus originates from its interior or from its surface. It is found that the surface part of a heavy nucleus contributes dominantly to its symmetry energy compared to its inner part. The symmetry energy coefficient asym(A) is then directly extracted and the ratio of the surface symmetry coefficient to the volume symmetry coefficient κ is estimated. Meanwhile, with the help of experimental alpha-decay energies, a macroscopic method is developed to determine the symmetry energy coefficient of heavy nuclei. The resultant asym(A) is used to analyze the density dependence of the symmetry energy coefficient of nuclear matter around the saturation density, and furthermore, the neutron skin thickness of 208Pb is deduced which is consistent with the pygmy dipole resonance analysis. In addition, it is shown that the ratio κ obtained from the macroscopic method is in agreement with that from the Skyrme energy density functional. Thus the two completely different approaches may validate each other to achieve more compelling results. © 2013 American Physical Society. Source

Xiao X.,University of Chinese Academy of Sciences | Liu X.,University of Chinese Academy of Sciences | Zhao H.,University of Chinese Academy of Sciences | Chen D.,China Institute of Atomic Energy | And 4 more authors.
Advanced Materials

Co3O4 with three different crystal plane structures - cubes bounded by {001}planes, truncated octahedra enclosed by {111} and {001} planes, and octahedra with exposed {111}planes - is synthesized using a very simple one-step hydrothermal method. The three kinds of Co3O 4 exhibit significantly different electrochemical performances and the effect of different exposed crystal planes on the electrochemical performance of Co3O4 is comprehensively studied. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Liu Z.-H.,China Institute of Atomic Energy | Bao J.-D.,Beijing Normal University | Bao J.-D.,Accelerator Centre
Physical Review C - Nuclear Physics

Synthesis of element 120 in the 249Cf(50Ti,xn)299-x120 and 248Cm(54Cr,xn)302-x120 fusion evaporation reactions has been evaluated by means of a modified fusion by diffusion model. It is found that the fusion probability of the system 54Cr+248Cm is two times smaller than that of 50Ti+249Cf. On the other hand, the survival probability of the former is obviously greater than that of the latter. As a result, the loss in the fusion probability of the 54Cr+248Cm reaction is compensated by its gain in survival probability. The calculated maximum evaporation residue cross sections in the 249Cf(50Ti,3n)296120 and 248Cm(54Cr,4n)298120 reactions are quite close: 0.034 and 0.024 pb, respectively. Besides, as compared to the system 50Ti+249Cf, the 54Cr+248Cm combination has two advantages. First, 248Cm is much easier accumulate a sufficient amount for the target material than 249Cf. Second, the isotope 298120 has 178 neutrons, two neutrons more than the isotope 296120. Therefore, the 54Cr+248Cm combination should be one of most favorable candidates to produce superheavy element 120. © 2013 American Physical Society. Source

Wang N.,Guangxi Normal University | Liu M.,Guangxi Normal University | Wu X.,China Institute of Atomic Energy | Meng J.,Beijing University of Technology | Meng J.,Beihang University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

By taking into account the surface diffuseness correction for unstable nuclei, the accuracy of the macroscopic-microscopic mass formula is further improved. The rms deviation with respect to essentially all the available mass data falls to 298 keV, crossing the 0.3 MeV accuracy threshold for the first time within the mean-field framework. Considering the surface effect of the symmetry potential which plays an important role in the evolution of the "neutron skin" toward the "neutron halo" of nuclei approaching the neutron drip line, we obtain an optimal value of the symmetry energy coefficient J = 30.16 MeV. With an accuracy of 258 keV for all the available neutron separation energies and of 237 keV for the α-decay Q-values of super-heavy nuclei, the proposed mass formula is particularly important not only for the reliable description of the r process of nucleosynthesis but also for the study of the synthesis of super-heavy nuclei. © 2014 The Authors. Source

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