Hong-Fei Zhang

Spontaneous fission half-lives of heavy and superheavy nuclei within a generalized liquid drop model

We systematically calculate the spontaneous fission half-lives for heavy and superheavy nuclei between U and Fl isotopes. The spontaneous fission process is studied within the semi-empirical WKB approximation. The potential barrier is obtained using a generalized liquid drop model, taking into account the nuclear proximity, the mass asymmetry, the phenomenological pairing correction, and the microscopic shell correction. Macroscopic inertial-mass function has been employed for the calculation of the fission half-life. The results reproduce rather well the experimental data. Relatively long half-lives are predicted for many unknown nuclei, sufficient to detect them if synthesized in a laboratory.

Dense nuclear matter and symmetry energy in strong magnetic fields

Abstract The properties of nuclear matter in the presence of a strong magnetic field, including the density-dependent symmetry energy, the chemical composition and spin polarizations, are investigated in the framework of the relativistic mean field models FSUGold. The anomalous magnetic moments (AMM) of the particles and the nonlinear isoscalar–isovector coupling are included. It is found that the parabolic isospin dependence of the energy per nucleon of asymmetric nuclear matter remains valid for the values of magnetic field below 10 5 B c e , B c e = 4.414 × 10 13 G being the electron critical field. Accordingly, the symmetry energy can be obtained by the difference of the energy per nucleon in pure neutron matter and that in symmetric matter. The symmetry energy, which is enhanced by the presence of the magnetic field, significantly affects the chemical composition and the proton polarization. The effects of the AMM of each component on the energy per nucleon, symmetry energy, chemical composition and spin polarization are discussed in detail.

Spectroscopic factor and proton formation probability for the d3/2 proton emitter 151mLu

Abstract The quenching of the experimental spectroscopic factor for proton emission from the short-lived d 3 / 2 isomeric state in 151mLu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyvaskyla. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151mLu.

Nuclear Stopping and Pauli Blocking in Heavy-Ion Reactions near Fermi Energy*

The dissipation phenomenon in the heavy-ion reaction at incident energy near the Fermi energy is studied by simulating the reaction 129Xe+129Sn with the isospin-dependent quantum molecular dynamics model. The calculations involving a proper prescription of implementing the Pauli exclusion principle show that the isotropy ratio measured by free protons emitted in the reaction at energy slightly higher than the Fermi energy is in agreement with the experimental data recently released by the INDRA collaboration. A feasible value of the Pauli-blocking factor is estimated by comparing the theoretical results with the experimental data for the energy range considered here.

A statistical approach to describe highly excited heavy and superheavy nuclei

A statistical approach based on the Weisskopf evaporation theory has been developed to describe the de excitation process of highly excited heavy and superheavy nuclei, in particular for the proton-rich nuclei. The excited nucleus is cooled by evaporating gamma-rays, light particles (neutrons, protons, alpha 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 Si-28+Pt-198 reaction can be reproduced nicely within the approach.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 28Si+198Pt reaction can be reproduced nicely within the approach.

Production of proton-rich nuclei around Z = 84-90 in fusion-evaporation reactions

Abstract.Within the framework of the dinuclear system model, production cross sections of proton-rich nuclei with charged numbers of Z = 84-90 are investigated systematically. Possible combinations with the 28Si, 32S, 40Ar bombarding the target nuclides 165Ho, 169Tm, 170-174Yb, 175,176Lu, 174, 176-180Hf and 181Ta are analyzed thoroughly. The optimal excitation energies and evaporation channels are proposed to produce the proton-rich nuclei. The systems are feasible to be constructed in experiments. It is found that the neutron shell closure of N = 126 is of importance during the evaporation of neutrons. The experimental excitation functions in the 40Ar induced reactions can be nicely reproduced. The charged particle evaporation is comparable with neutrons in cooling the excited proton-rich nuclei, in particular for the channels with

Correlation between muonic levels and nuclear structure in muonic atoms

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Isospin splitting of nucleon effective mass and symmetry energy in isotopic nuclear reactions

α and proton evaporation. The production cross section increases with the mass asymmetry of colliding systems because of the decrease of the inner fusion barrier. The channels with pure neutron evaporation depend on the isotopic targets. But it is different for the channels with charged particles and more sensitive to the odd-even effect.

Nuclear stopping power evaluated via free protons emitted in reaction Xe+Sn near fermi energy

Abstract A method that deals with the nucleons and the muon unitedly is employed to investigate the muonic lead, with which the correlation between the muon and nucleus can be studied distinctly. A “kink” appears in the muonic isotope shift at a neutron magic number where the nuclear shell structure plays a key role. This behavior may have very important implications for the experimentally probing the shell structure of the nuclei far away from the β -stable line. We investigate the variations of the nuclear structure due to the interaction with the muon in the muonic atom and find that the nuclear structure remains basically unaltered. Therefore, the muon is a clean and reliable probe for studying the nuclear structure. In addition, a correction that the muon-induced slight change in the proton density distribution in turn shifts the muonic levels is investigated. This correction to muonic level is as important as the Lamb shift and high order vacuum polarization correction, but is larger than anomalous magnetic moment and electron shielding correction.

NUCLEON-NUCLEON CROSS SECTIONS IN ISOSPIN ASYMMETRIC NUCLEAR MATTER

Within an isospin and momentum dependent transport model, the dynamics of isospin particles (nucleons and light clusters) in Fermi-energy heavy-ion collisions are investigated for constraining the isospin splitting of nucleon effective mass and the symmetry energy at subsaturation densities. The impacts of the isoscalar and isovector parts of the momentum dependent interaction on the emissions of isospin particles are explored, i.e., the mass splittings of m_n~*=m_p~* and m_n~*>m_p~* (m_n~*<m_p~*). The single and double neutron to proton ratios of free nucleons and light particles are thoroughly investigated in the isotopic nuclear reactions of 112Sn+112Sn and 124Sn+124Sn at incident energies of 50 and 120 MeV/nucleon, respectively. It is found that both the effective mass splitting and symmetry energy impact the kinetic energy spectra of the single ratios, in particular at the high energy tail (larger than 20 MeV). The isospin splitting of nucleon effective mass slightly impacts the double ratio spectra at the energy of 50 MeV/nucleon. A soft symmetry energy with stiffness coefficient of γ_s=0.5 is constrained from the experimental data with the Fermi-energy heavy-ion collisions.