Synthesis of superheavy nuclei with <Superscript>238</Superscript>U target

The production of superheavy nuclei with Z=108-116 via hot fusion reactions of the neutron-rich projectiles with 238U target is systematically studied.The results show that the production cross sections of superheavy nuclei do not decrease monotonously as the atomic number Z increasing.The cross sections of the superheavy nuclei at Z = 112 and 115 are enhanced as compared with the whole Z-trend in synthesis of the superheavy nuclei,which clearly illustrates that the reactions with large negative Q-value and...     

超重核294118和291116及其α衰变链上各核素半衰期的研究

运用推广的液滴模型（GLDM）确定了超重核294118和291116及其α衰变链上各核素的衰变势垒, 采用量子力学中的WKB方法计算α衰变中的势垒穿透几率, 对该链上各原子核的α衰变半衰期进行了研究。 此外, 还利用Royer公式对该链上各原子核的α衰变半衰期进行了计算。 结果表明, GLDM 考虑亲和能与Royer公式给出的α衰变半衰期与超重核区的实验值符合很好, 验证了GLDM和Royer公式在超重核区的适用性,可以用来预测超重核的半衰期。 最后, 预言了Z=118 和116 同位素链上各核素的半衰期, 结果表明, 在Z=118和116中存在α衰变长寿命同位素, 这需要实验上的检验。The α decay potential barrier of the newly synthesized superheavy nuclei starting from 294118 and 291116 have been determined and their half lives have been studied with the Generalized Liquid Drop Model(GLDM) connected with WKB approximation and Royer’s formulae．The α decay half lives of the nuclei belonging to the superheavy nuclei starting from 294118 and 291116 have been calculated．The calculated results are in agreement with the experimental data, which show that the α decay half lives of superheavy nuclei with the GLDM and Royer’s formulae can be applied in the studying on superheavy nuclei successfully．Finally, the half lives of Z=118 and 116 isotopes have been predicted, and the results suggest there may be some long lived superheavy nuclei for α decay in those isotopes.     

用宏观-微观模型系统计算偶-偶超重核基态性质

用宏观--微观模型系统计算了Z=94—112偶偶超重核的基态性质. 其中宏观部分基于液滴模型, 微观部分采用改进的谐振子势. 理论计算的结合能、α衰变能 与已知的实验数据符合, 理论计算结果也与Moller的计算结果符合很好.这肯定了宏观--微观模型对超重核性质研究的可靠性和稳定性. 对一些未知核素基态性 质的预言可为将来的实验研究提供理论参考.     

热熔合反应合成超重核产生截面的同位素依赖性

通过在形成超重核的重离子俘获和熔合过程中引入位垒分布函数的方法对双核模型做了进一步发展. 超重核形成过程中的俘获、熔合和蒸发3个阶段分别采用了半经验的耦合道模型、数值求解主方程和统计蒸发模型的方法来描述. 计算了近年来Dubna小组利用热熔合反应⁴⁸Ca(²⁴³Am, 3n—5n)^288—286115和⁴⁸Ca(²⁴⁸Cm, 3n—5n)^293—291116合成超重新核素的蒸发余核激发函数. 系统分析了⁴⁸Ca轰击锕系元素U,Np,Pu,Am,Cm合成超重核Z=112—116产生截面的同位素依赖性. 给出了合成超重新核素最佳的弹靶组合和入射能量, 即有最大的超重核产生截面. 计算说明, 壳修正能和中子分离能是影响超重核生成截面产生同位素依赖性的主要因素.     

Search for decay modes of heavy and superheavy nuclei

Spontaneous fission(SF) with a new formula based on a liquid drop model is proposed and used in the calculation of the SF half-lives of heavy and superheavy nuclei(Z = 90–120). The predicted half-lives are in agreement with the experimental SF half-lives. The half-lives of decay(AD) for the same nuclei are obtained by using the Wentzel-Kramers-Brillouin(WKB) method together with Bohr-Sommerfeld(BS) quantization condition considering the isospin-dependent effects for the cosh potential. The decay modes and branching ratios of superheavy nuclei(Z =104-118) with experimental decay modes are obtained, and the modes are compared with the experimental ones and with the predictions found in the literature. Although some nuclei have predicted decay modes that are different from their experimental decay modes, decay modes same as the experimental ones are predicted for many nuclei. The SF and AD half-lives, branching ratios, and decay modes are obtained for superheavy nuclei(Z = 119–120) with unknown decay modes and compared with the predictions obtained in a previous study. The present results provide useful information for future experimental studies performed on both the AD and SF of superheavy nuclei.     

Determination of Charges of Superheavy Nuclei in Finding them in Nature

Bulletin of the Lebedev Physics Institute - The results of the search for tracks of heavy and superheavy nuclei of galactic cosmic rays in the charge range Z = 26 ? 129, identified in olivine...     

超重核α衰变寿命的理论研究

建立了计算球形核α衰变寿命的新模型——密度依赖的结团模型(DDCM)。在此基础上,通过引入子核的形变自由度,发展了形变的密度依赖的结团模型, 编写了形变的DDCM程序。并系统计算了Z=106—110的超重核α衰变寿命。通过与已有的实验数据的对比分析, 发现理论结果和实验数据符合得很好,验证了DDCM在超重核区域的适用性。We proposed a deformed version of density dependent cluster model (DDCM) by including nuclear deformation of the daughter nucleus. A systematic calculation of α decay half lives of superheavy nuclei (Z=106—110) is carried out by the deformed DDCM. The good agreement between theory and data is obtained. It is shown that the deformed DDCM works well in the superheavy mass region.     

A Detail Investigation on the Synthesis of Superheavy Element Z = 119

Physics of Particles and Nuclei Letters - We have studied the α-decay properties of superheavy nuclei Z = 119 in the range 265 ≤ A ≤ 316. By studying the α-decay properties,...     

Origin of Unexpected Isotopic Trends in Synthesis of Superheavy Nuclei

We investigate the dependence of the yield of superheavy nuclei with Z = 110, 112, 114 on the neutron excess of the projectile nucleus with a two-parameter Smoluchowski equation. It is confirmed that in some cases, the cold fusion reactions with less neutron excess are more favourable than those with more neutron excess. In order to probe the origin of these unexpected isotopic trends, we also investigate the probabilities of capture, fusion and survival in the cold fusion reactions in detail It is found that the maximal ER cross sections of the superheavy nuclei exponentially increase as a function of Bf - Sn with Bf being the fission barrier and Sn being the neutron separation energy. Although the probabilities of capture and fusion have some influences, the unexpected isotopic trends mainly due to the dependence of the ER cross sections on the Bf - Sn value. Therefore, the reactions with larger Bf - Sn values should be more favourable for synthesis of superheavy nuclei.     

A self-consistent mean-field study of Z = 120 nuclei and α-decay chains of 292,298,299,300,304120 isotopes

A self-consistent mean-field investigation is done to test the model accuracy, model dependence, and the dependence on different model parameters in the study of superheavy nuclei. This is done within the self-consistent mean-field models-the Skyrme-Hartree-Fock-Bogoliubov (HFB), and the Relativistic-Hartree-Bogoliubov (RHB) with density-dependent couplings. A systematic comparison is made with experimental data, as well as with the macro-microscopic Finite Range Droplet Model(FRDM). The bulk ground state properties and the microscopic structure of Z=120 superheavy nuclei are investigated. Further investigation is made of α-decay series for the five isotopes ^{292,298,299,300,304}120 of Z=120 nuclei. A spontaneous fission investigation is done to account the number of α-decay before spontaneous fission starts. The experimental data available for α-decay energies and half-lives are produced reasonably. The RHB model with NL3* parameter set, and with ImSahu and UNIV2 formula to calculate the α-decay half-lives is found to be the best suited for accurately predicting the ground state properties and the α-decay half-lives of the superheavy nuclei.     

偶-偶超重核基态性质的理论研究

在形变的相对论平均场模型下采用NL Z2,TMA两套参数对一些偶 偶核基态性质进行了系统的计算,并将理论计算的结合能、α衰变能与已知的实验数据进行了对比分析.结果发现两方面的数据能够比较好地吻合,从而验证了相对论平均场模型对超重核研究是可行的.同时在计算中给出了未知核素基态性质的计算结果,可供以后在理论或实验上研究超重核时参考. The ground state properties of the even even nuclei with proton number Z=94-104 have been systematically calculated in the deformed relativistic mean field (RMF) theory with two sets of force parameters, TMA and NL Z2. Comparing the calculated binding energies and alpha decay energys with the experimental ones, it is found that theoretical results are in good agreement with experimental data. The reliability of the RMF model for even even superheavy nuclei has been tested by this comparison...     

Superheavy nuclei in deformed mean--field calculations

The ground–state properties of superheavy nuclei are investigated within various parametrisations of relativistic and nonrelativistic nuclear mean–field models. The heaviest known even–even nuclei starting with Z = 98 are used as a benchmark to estimate the predictive power of the models and forces. From that starting point, deformed doubly magic nuclei are searched in the region 100 ≤ Z ≤ 130 and 142 ≤ N ≤ 190. Received: 6 April 1998 / Revised version: 16 June 1998     

Systematic study of survival probability of excited superheavy nuclei

The stability of excited superheavy nuclei (SHN) with 100 Z 134 against neutron emission and fission is investigated by using a statistical model. In particular, a systematic study of the survival probability against fission in the 1n-channel of these SHN is made. The present calculations consistently take the neutron separation energies and shell correction energies from the calculated results of the finite range droplet model which predicts an island of stability of SHN around Z = 115 and N = 179. It turn...     

基于相对论平均场理论对超重核冷熔合反应截面的研究

在形变约束的相对论平均场理论框架下计算了合成Z=102—118元素的(可能)冷熔合反应中复合核及蒸发一或两个中子剩余核的位能曲面,得到了复合核和剩余核平衡点和鞍点的性质、静态裂变垒高度和冷熔合反应的最佳入射能;利用壳修正和对修正方法计算了平衡点和鞍点的壳修正能、对修正能和微观能.利用由此得到的壳结构信息,用简单的熔合蒸发唯象模型计算了相应反应的冷熔合截面.结果发现,TM1参数提供的结构性质给出了与实验接近的反应截面.     

相对论平均场模型对奇-偶超重核基态性质的系统研究

在形变的相对论平均场模型下,采用NL-Z2,TMA两套参数对质子数为103—109的奇–偶核基态性质进行了系统的计算,并将理论计算的结合能、α衰变能与已知的实验数据进行对比,发现两者符合得很好,肯定了相对论平均场模型对超重核研究的可靠性,同时对未知核素基态性质的计算结果可供未来的超重核理论和实验研究参考.     

Binding energies of even-even superheavy nuclei

The structure of the even-even superheavy nuclei with the proton number Z=98–110 is studied using the self-consistent relativistic mean-field theory. The calculated binding energies are in good agreement with the available experimental ones. An upper limit and a lower limit on the binding energies are set by the calculations. This is useful for future calculations of properties of superheavy nuclei and for the experimental synthesis of superheavy nuclei. The energy surface of some relevant superheavy nuclei is also given and it confirms the correctness of the calculations.     

Predictions of synthesizing element 119 and 120

The evaporation residue cross sections of synthesizing superheavy nuclei Z=119, 120 are calculated by different sets of master equations with different dynamical variables. Two methods basically predicted similar results that the Ca induced hot fusion can 48 produce element 119 easier than produce 120, and the evaporation residue cross sections for 119 are detectable by current advanced techniques, while the evaporation residue cross sections are below 0.1 pb for producing element 120.     

不同理论模型预言合成超重核Z=119~122研究进展

通过双核系统模型与其他模型对$Z\leqslant$118元素的计算结果与实验数据的比较,证明了不同模型预测超重核的产生截面是可靠的。对比分析了不同模型对Z=119和Z=120超重核的预言结果,我们认为合成超重核Z=119和Z=120的最佳弹靶组合分别为反应$^{48}{\rm{Ca}} + ^{{\rm{252}}}{\rm{Es}}$和$^{40}{\rm{Ca}} + ^{{\rm{257}}}{\rm{Fm}}$,并且Z=119新核素很有可能会先于Z=120新核素在实验上被合成。由于实验上Z>100锕系靶的限制,人们正尝试寻找比48Ca更重的弹核来合成超重核Z=121和Z=122,超重核Z=121可以通过反应V+Cf来合成,而超重核Z=122的产生截面已经非常小,要求将来在实验上提高探测及鉴别技术。希望本文的讨论可以在将来为实验及理论核物理工作者们提供一些参考。     

Heavy-particle radioactivity of superheavy nuclei

The concept of heavy-particle radioactivity (HPR) is changed to allow emitted particles with Z(e) > 28 from parents with Z > 110 and daughter around (208)Pb. Calculations for superheavy (SH) nuclei with Z = 104-124 are showing a trend toward shorter half-lives and larger branching ratio relative to α decay for heavier SHs. It is possible to find regions in which HPR is stronger than alpha decay. The new mass table AME11 and the theoretical KTUY05 and FRDM95 masses are used to determine the released energy. For 124 we found isotopes with half-lives in the range of ns to ps.