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A statistical approach based on the Weisskopf evaporation theory has been developed to describe the deexcitation process of highly excited heavy and superheavy nuclei, in particular for the proton-rich nuclei. The excited nucleus is cooled by evaporating γ-rays, light particles(neutrons, protons, α etc) in competition with binary fission,in which the structure effects(shell correction, fission barrier, particle separation energy) contribute to the processes.The formation of residual nuclei is evaluated via sequential emission of possible particles above the separation energies.The available data of fusion-evaporation excitation functions in the ~(28)Si+~(198)Pt reaction can be reproduced nicely within the approach. 相似文献
63.
We search for signatures of Lorentz and violations in the cosmic microwave background (CMB) temperature and polarization anisotropies by using the Wilkinson Microwave Anisotropy Probe (WMAP) and the 2003 flight of BOOMERANG (B03) data. We note that if the Lorentz and symmetries are broken by a Chern-Simons term in the effective Lagrangian, which couples the dual electromagnetic field strength tensor to an external four-vector, the polarization vectors of propagating CMB photons will get rotated. Using the WMAP data alone, one could put an interesting constraint on the size of such a term. Combined with the B03 data, we found that a nonzero rotation angle of the photons is mildly favored: [Formula: See Text]. 相似文献
64.
DONG Jian-Min ZHANG Hong-Fei WANG Yan-Zhao ZUO Wei SU Xin-Ning LI Jun-Qing 《中国物理C(英文版)》2009,33(8):633-638
The generalized liquid drop model (GLDM) and the cluster model have been employed to calculate the α-decay half-lives of superheavy nuclei (SHN) using the experimental α-decay Q values. The results of the cluster model are slightly poorer than those from the GLDM if experimental Q values are used. The prediction powers of these two models with theoretical Q values from Audi et al. (Qaudi) and Muntian et al. (QM) have been tested to find that the cluster model with Qaudi and QM could provide reliable results for Z>112 but the GLDM with Qaudi for Z≤112. The half-lives of some still unknown nuclei are predicted by these two models and these results may be useful for future experimental assignment and identification. 相似文献
65.
We investigate the dependences of the potential energy surfaces (PES) and the fusion probabilities for some cold fusion reactions leading to super-heavy elements on the nuclear shell effect and pairing energy. It is found that the shell effect plays an important role in the fusion of the super-heavy element while pairing energy's contribution is insignificant. The fusion probabilities and evaporation residue cross sections as functions of the Ge-isotope projectile bombarding ^208Pb are also investigated. It is found that evaporation residue cross sections do not always increase with the increasing neutron number of Ge-isotope. 相似文献
66.
The restriction of the one dimensional (1D) master equation (ME) with the mass number of the projectile-like fragment as a variable is studied, and a two-dimensional (2D) master equation with the neutron and proton numbers as independent variables is set up, and solved numerically. Our study showed that the 2D ME can describe the fusion process well in all projectile target combinations. Therefore the possible channels to synthesize super-heavy nuclei can be studied correctly in wider possibilities. The available condition for employing 1D ME is pointed out. 相似文献
67.
The generalized liquid drop model (GLDM), including the proximity effects and centrifugal potential, and the cluster model with Cosh potential are used to study the half-lives of some Z = 113 isotopes and their α-decay products. The experimental half-lives of 284^113, 283^113, 282^113 and their α-decay products are well reproduced by the two models when zero angular momenta transfer is assumed. For 278^113 and its α-decay products, both the GLDM and the duster model could provide satisfactory results if we assume the α particle carry five units of angular momenta, which indicates that possible nonzero angular momenta transfer and need further experimental measurements with high precision. Finally, we show that half-lives of α-decay are quite sensitive to the angular momentum transfers, and a formula could be used to describe the correlation between α-decay half-life and angular momentum transfer successfully. 相似文献
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69.
以水杨醛与1,2-二溴乙烷为反应物, 乙腈为溶剂, 在无水K2CO3存在下合成了2-溴乙氧基水杨醛(1), 1和二-(1,3-二硫杂环戊烯-2-硫酮-4,5-二硫)合锌酸四乙基铵盐在乙腈中回流, 得到新型的四硫富瓦烯(TTF)前体(2). 在Hg(OAc)2存在下, 2可转化为4,5-二[2-(邻甲酰苯氧基)乙硫基]-1,3-二硫环戊烯-2-酮(3), 其结构经1H NMR, FT-IR, 元素分析和单晶X射线衍射分析得到确证. 相似文献