Shell Effect of Superheavy Nuclei in Self-consistent Mean-Field Models

We analyze in detail the numerical results of superheavy nuclei in deformed relativistic mean-field model and deformed Skyrme-Hartree-Fock model. The common points and differences of both models are systematically compared and discussed. Their consequences on the stability of superheavy nuclei are explored and explained. The theoretical results are compared with new data of superheavy nuclei from GSI and from Dubna and reasonable agreement is reached. Nuclear shell effect in superheavy region is analyzed and discussed. The spherical shell effect disappears in some cases due to the appearance of deformation or superdeformation in the ground states of nuclei, where valence nucleons occupy significantly the intruder levels of nuclei. It is shown for the first time that the significant occupation of valence nucleons on the intruder states plays an important role for the ground state properties of superheavy nuclei. Nuclei are stable in the deformed or superdeformed configurations. We further point out that one cannot obtain the octupole deformation of even-even nuclei in the present relativistic mean-field model with the σ, ω and ρ mesons because there is no parity violating interaction and the conservation of parity of even-even nuclei is a basic assumption of the present relativistic mean-field model.

宇称不守恒的第一个验证实验——吴健雄钴-60极化核β衰变实验

1957年1月,一个震撼世界实验结果:“钴-60极化核β衰变不对称性”——证明了“弱相互作用中宇称不守恒”。提出宇称不守恒理论的杨振宁和李政道教授,荣获当年诺贝尔物理学奖! 物理学是一门实验科学。任何理论没有实验证实,是不会为人们接受的。杨振宁和李政道教授正是因为有另一位中国留美核物理学家,有“核子物理女皇”、“世界最杰出的女性实验物理学家”和“中国居里夫人”等盛誉的吴健雄教授,很快就主持作出确凿的实验验证,才得以创造科学史上伟大的奇迹。因而众多诺贝尔物理奖得主都认为,“吴健雄绝对应该和杨振宁、李政道同时获得诺贝尔物理学奖”。在此新世纪新千年到来之时,让我们同时回顾一下誉满全球的吴健雄教授,主持作出第一个验证实验的辉煌科学道路,

袁家骝:世界科技星宿

1997年4月6日,著名美籍华人物理学家袁家骝博士,怆然不顾84岁高龄,专程从美国飞抵江苏省太仓市浏河镇——其夫人“世界物理女王”、“核子物理学首席物理学家”、美籍华人科学家吴健雄博士的故乡,将今年2月17日在纽约逝世的吴健雄博士的骨灰护送回故里,安放在浏河镇明德学校明德楼,参加了太仓市政府当晚22时在那里隆重举行的安放追悼仪式,了遂吴健雄的遗愿。江苏省副省长张怀西、省侨办副主任丛建国、苏州市侨办主任吴嘉哲等参加了仪式。

Theoretical Analysis of Neutron Double-Differential Cross Section of n ＋^19F at 14.2 MeV

A new light nuclear reaction model has been developed and the double-differential measurements of lp shell nuclei have been analyzed successfully. Now, the application of this model is expanded to 19F of the 2s-ld shell nucleus. The double-differential cross section of total outgoing neutron for n ＋^19F reactions at En=14.2 MeV has been calculated and analyzed, which agrees fairly well with the experimental measurements. In this paper, the contributions from different reaction channels to the double-differential cross sections have been analyzed in detail. The calculations indicate that this light nudear reaction model is also able to be used for the 2s-ld shell nucleus so long as the related level scheme couM be provided sufficiently.

Relativistic Consistent Angular-Momentum Projected Shell-Model： Relativistic Mean Field

We develop a relativistic nuclear structure model, relativistic consistent angular-momentum projected shell-model (RECAPS), which combines the relativistic mean-field theory with the angular-momentum projection method. In this new model, nuclear ground-state properties are first calculated consistently using relativistic mean-field (RMF) theory. Then angular momentum projection method is used to project out states with good angular momentum from a few important configurations. By diagonalizing the hamiltonian, the energy levels and wave functions are obtained. This model is a new attempt for the understanding of nuclear structure of normal nuclei and for the prediction of nuclear properties of nuclei far from stability. In this paper, we will describe the treatment of the relativistic mean field. A computer code, RECAPS-RMF, is developed. It solves the relativistic mean field with axial-symmetric deformation in the spherical harmonic oscillator basis. Comparisons between our calculations and existing relativistic mean-field calculations are made to test the model. These include the ground-state properties of spherical nuclei 16O and 208Pb, the deformed nucleus 20Ne. Good agreement is obtained.

Comment on Revision of Kaup-Newell's Works on IST for DNLS Equation

In this note, it is shown that the revision of the Kaup-Newell＇s works on 1ST for DNLS equation is only available in the ease of solving the bright one-soliton solution to the equation. An example is taken to illustrate our point of view.

Influence of Isotope on Shell Effects of Pre-scission Particle Evaporation

The shell effects on the particle evaporation prior to fission for three Pb isotopes, ^204Pb, ^208Pb, and ^212pb,as well as three Sn isotopes, ^128Sn, ^132Sn, and ^136Sn, are explored by a diffusion model. Calculations show that the magnitude of shell effects in the emission of particles changes with the neutron-to-proton ratio N/Z of these fissioning nuclei, and this change is affected significantly by the spin and excitation energy of the system. It is shown that high angular momentum enhances the dependence of shell effects on the N/Z while high excitation energy weakens such a dependence.

Antikaon Condensation and In-medium Kaon and Antikaon Production in Protoneutron Stars

Antikaon condensation and kaon and antikaon production in protoneutron stars are investigated in a chiral hadronic model （also referred to as the FST model in this paper）. The effects of neutrino trapping on protoneutron stars are analyzed systematically. It is shown that neutrino trapping makes the critical density of K^- condensation delay to higher density and fifo condensation not occur. The equation of state （EOS） of （proto）neutron star matter with neutrino trapping is stiffer than that without neutrino trapping. As a result, the maximum masses of （proto）neutron stars with neutrino trapping are larger than those without neutrino trapping. If hyperons are taken into account, antikaon does not form a condensate in （proto）neutron stars. Meanwhile, the corresponding EOS becomes much softer, and the maximum masses of （proto）neutron stars are smaller than those without hyprons. Finally, our results illustrate that the Q values for K^＋ and K^- production in （proto）neutron stars are not sensitive to neutrino trapping and inclusion of hyperons.

Topological Excitation in Skyrme Theory

Based on the C-mapping topological current theory and the decomposition of gauge potential theory, we investigate knotted vortex lines and monopoles in Skyrme theory and simply discuss the branch processes （splitting, merging, and intersection） during the evolution of the monopoles.

The Role of Potential Structure in Excitation Functions of Synthesizing Superheavy Nuclei

The excitation functions of two very similar reaction channels, 58Fe＋ 208pb→ 265Hs ＋ 1n and 58Fe＋ 209Bi → 266Mt ＋1n are studied in the framework of the dinuclear system conception. The fusion probabilities are found to be strongly subject to the structure of the driving potential. Usually the fusion probability is hindered by a barrier from the injection channel towards the compound nuclear configuration. The barrier towards the mass symmetrical direction, however, also plays an important role for the fusion probability, because the barrier hinders the quasi-fission, and therefore helps fusion.

K^- Nucleus Elastic Scattering and Momentum-Dependent Optical Potentials

The K? nucleus differential elastic scattering cross section for 12C and 40Ca at is calculated with three momentum-dependent optical potential models, which are density-dependent, relativistic mean field, and hybrid model, respectively. It is found that the forms of momentum-dependent optical potential models proposed by us are reasonable and gain success in the calculations and the momentum-dependent hybrid model is the best model for the K? nucleus elastic scattering.

A Detailed Study of Pre-scission γ Emission as a Probe of Nuclear Dissipation

Using a Langevin equation coupled with a statistical model, we calculate pre-scission giant dipole resonance （GDR） γ-ray multiplicity of nuclei 194 pb, 200Pb, 206Pb, and 200 Os. It is demonstrated that with increasing the isospin asymmetry of these fissioning nuclei the sensitivity of the emitted γ multiplicity to the nuclear viscosity coefficient is decreased significantly. For 200Os nuc/eus, this γ-ray emission is no longer sensitive to the magnitude of the viscosity coefficient. In addition, the effect of the isospin asymmetry on the γ rays as a probe of nuclear dissipation is reduced with increasing angular momentum. These results suggest that to obtain a more accurate information of the viscosity coemfficient by the measurement of pre-scission GDR γ-ray multiplicity it is better to choose those compound systems with small isospin asymmetry and low spin.

Cooling Torsional Nanomechanical Vibration by Spin-Orbit Interactions

We propose and study a spin-orbit interaction based mechanism to actively cool down the torsional vibrationof a nanomechanical resonator made by semiconductor materials.We show that the spin-orbit interactions of electronscan induce a coherent coupling between the electron spins and the torsional modes of nanomechanical vibration.Thiscoupling leads to an active cooling for the torsional modes through the dynamical thermalization of the resonator by thespin ensemble.

QCD Approach to B→Dπ Decays and CP Violation

The branching ratios and CP violations of the B →Dπ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams that lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass μg is regarded as a universal sca/e, it is extracted to be around μg = 440 MeV from one of the well-measured B →Dπ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct CP asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the B →D^±π^±↓ decays to be consistent with the experimental data at 1-σ level. More precise measurements will be helpful to extracting weak angle 2β＋γ.

Formalism of Helicity Coupling Amplitudes for J/ψ→π^＋π^-π^0

The formalisms of helicity coupling amplitudes for J/ψ→π^＋π^-π^0 are presented. A detailed discussion is also given on the barrier factor, Breit Wigner, and density matrix. A Monte Carlo simulation of J/ψ→ρ（770）π→π^＋π^-π^0 is carried out. The results show that the p（770） resonance is well reproduced compared with experimental data.

The Interacting Boson Model of Dipole—Octupole Strong Correlations in SU（3） Limit for Positive Parity States

Within the framework of the Usdpf(16) interacting boson model (IBM), the effects of strong correlations of the dipole (p?-boson) and the octupole (f?-boson) degree of freedom on the positive-parity states of even-even nuclei in SU(3) limit are discussed. It is shown that configurations of an even number of many p- and f-bosons can not only be incorporated into the usual low-lying collective rotational bands, such as the ground state band, β- and γ-vibrational bands, but also naturally form the rotational bands, etc. These results are similar to that of Usdg(15)-IBM and in good agreement with the experimental data of the nucleus. Besides, several intraband E2 transition probabilities are given, which are consistent with that of Usd(6)-IBM.

Effects of Isospin on Pre-scission Particle Multiplicity of Heavy Systems and ItsExcitation Energy Dependence

Isospin effects on particle emission of fissioning isobaric sources and isotopic sources , and its dependence on the excitation energy are studied via Smoluchowski equations. It is shown that with increasing the isospin of fissioning systems, charged-particle emission is not sensitive to the strength of nuclear dissipation. In addition, we have found that increasing the excitation energy not only increases the influence of nuclear dissipation on particle emission but also greatly enhances the sensitivity of the emission of pre-scission neutrons or charged particles to the isospin of the system. Therefore, in order to extract dissipation strength more accurately by taking light particle multiplicities it is important to choose both a highly excited compound nucleus and a proper kind of particles for systems with different isospins.

Description of Rotation Bands in ^(157,158)Er at Ultrahigh Spin

Properties of the four rotation bands, ^157Er（1,2） and ^15SEr（1,2）, at ultrahigh spin are investigated within the supersymmetry scheme including many-body interactions and possessing the SO（5） （or SU（5）） symmetry on the rotational symmetry. Quantitatively good results of the 7-ray energies and the dynamical moments of inertia in the rotation bands in ^157 Er and ^158 Er at ultrahigh spin are obtained. We theoretically predict that the competition between the anti-pairing and pairing effects may exist in ^157 Er（1,2） and ^158Et（2） bands states. In ^158Er（1） band state, the favourepairing effects may exist and the SO（5） （or SU（5）） symmetry play a dominant role. There may be sphere coexisting with headecupole deformed in ^158Et（1） rotation band state.

Properties of Unsymmetrical Parabolic Confinement Potential Quantum Dot Qubit

On the condition of electric-LO phonon strong coupling in unsymmetrical parabolic confinement potential quantum dot （QD）, we obtain the eigenenergies of the ground state and the first-excited state, the eigenfunctions of the ground state, and the first-excited state by using variational method of Pekar type. This system in QD may be employed as a two-level quantum system-qubit. When the electron is in the superposition state of the ground state and the first-excited state, we obtain the time evolution of the electron density. The relations both the probability density of electron and the period of oscillation with the electron-LO-phonon coupling strength, the confinement strengths in the xy-plane and the z-direction are discussed.