Zhang Hu-Yong

Proton Halo or Skin in the Excited States of Light Nuclei

Properties of nuclei N-13,N-15 and B-9 are investigated in the relativistic mean-field theory with NLZ and NL3 force parameters. The calculated binding energies are very close to the experimental ones. The calculations show that the first excited state (1p(1/2)) in B-9, the first excited state (2s(1/2)) in N-13 and the second excited state (2s(1/2)) in N-15 are weakly bound. In particular, for N-13 and N-15, the proton density distributions in the two above excited states have a long tail and the rms radii of the last proton are greatly larger compared with their respective matter radii. It is predicted that a proton halo exists in the first excited state of N-13 and in the second excited state of N-15, respectively. It also indicates that the first excited state in B-9 is a proton skin state.

Study on excitation function and isospin dependencies of total reaction cross section via the Boltzmann-Uehling-Uhlenbeck model

The excitation function and isospin dependencies of sigma(R) have been investigated by using the Boltzmann-Uehling-Uhlenbeck (BUU) model with a square-type density distribution. When the width parameter of the square distribution is obtained by fitting sigma(R) at relativistic energies, the BUU-model can reproduce the experimental data at intermediate energies better than Glauber model. The systematical underestimation of sigma(R) at intermediate energy by Glauber model was removed out now by BUU calculation framework. It is also found that sigma(R) is sensitive to nuclear equation of state and sigma(NN)(in-medium). The difference factor d defined in text is sensitive to the nuclear structure such as neutron halo and neutron skin, etc.

Total reaction cross section in an isospin-dependent quantum molecular dynamics model

The isospin-dependent quantum molecular dynamics (IDQMD) model is used to study the total reaction cross section σR. The energy-dependent Pauli volumes of neutrons and protons have been discussed and introduced into the IDQMD calculation to replace the widely used energy-independent Pauli volumes. The modified IDQMD calculation can reproduce the experimental σR well for both stable and exotic nuclei induced reactions. Comparisons of the calculated σR induced by 11Li with different initial density distributions have been performed. It is shown that the calculation by using the experimentally deduced density distribution with a long tail can fit the experimental excitation function better than that by using the Skyrme-Hartree-Fock calculated density without long tails. It is also found that σR at high energy is sensitive to the long tail of density distribution.

Possible 1d(5/2) and 2s(1/2) level inversion in the proton-rich nucleus Al-23

The discovered proton halo nucleus of (23)AI is investigated in the nonlinear relativistic mean-field (RMF) model with deformation using the NL075 force parameter. It is shown that there is an energy inversion between the (5/2)(+)(202) and (1/2)(+)(211) orbitals in the (23)AI nucleus, which may produce a large enhancement of the reaction cross section compared with the neighbouring nuclei. Meanwhile, the NL075 force parameter may be better than the other RMF parameters for the calculation of the large deformed nucleus (23)AI.

Measurements of Total Reaction Cross Sections for Exotic Nuclei Close to the Proton Drip-line at Intermediate Energies and Observation of a Proton Halo in 27P

Measurements of the total reaction cross sections (sigma (R)) for some proton-rich nuclei (N = 11 - 15 isotones) on a carbon target at intermediate energies have been performed on the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. A larger enhancement of sigma (R) for P-27 has been observed than for its neighbours. Evidence for a proton halo in P-27 has been revealed in the Glauber analysis of the total reaction cross sections in terms of the difference factor d.

Measurements of total reaction cross section for light nuclei and evidence for the anomalous nuclear structure in C-15

Measurements of the total reaction cross section for C12-16, N14-17 and O16-18 on carbon target at intermediate energies were performed on RIBLL of HIRFL. A larger enhancement of sigma(n) for C-15 was observed than that for its neighbors. The analysis of these data indicates possible existence of an anomalous nuclear structure in C-15. A new quantity was suggested as the criterion to distinguish anomalous structure nuclei from normal nuclei.

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 parityviolating interaction and the conservation of parity of even-even nuclei is a basic assumption of the present relativistic mean-field model.

Structures of 17F and 17O, 17Ne and 17N in the Ground State and the First Excited State

The structures of two couples of mirror nuclei 17F and 17O, 17Ne and 17N in the ground state and in the first excited state are investigated using the relativistic mean-field approach. Two-proton halo in 17Ne in the first excited state and in the ground state and two-neutron halo in 17N in the first excited state are suggested. Meanwhile, one-proton halo in 17F in the first excited state and one-neutron halo in 17O in the first excited state are also suggested. The skin structure appears in 17F and 17N in the ground state.

One-Proton Halo in 31Cl with Relativistic Mean-Field Theory

We investigate proton-rich isotopes 31,32Cl using the nonlinear relativistic mean-field model. It is shown that this model can reproduce the properties of these nuclei well. A long tail appears in the calculated proton density distribution of 31Cl. The results of relativistic density-dependent Hartree theory show a similar trend of tail density distribution. It is strongly suggested that there is a proton halo in 31Cl and it is indicated that there may be a proton skin in 32Cl. The relation between the proton halo in 31Cl and the new proton magic number is discussed.

Total reaction cross section measurements at intermediate energy for the proton halo candidate Al-23 and its neighbours

Total reaction cross sections sigma (R) for some proton-rich isotones (N = 10) near Al-23 on a carbon target have been measured at intermediate energies in the experiment performed at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. The Z-dependence Of sigma (R) shows a remarkable enhancement for Al-23 relative to its neighbours. The difference factor d has been deduced from the measured sigma (R) by using the Glauber or Boltzmann-Uehling-Uhlenbeck models. From the above analysis, a possible one-proton halo structure is suggested for Al-23.