Wei Yi-Bin

Isoscaling of projectile-like fragments

In this paper, the isotopic and isotonic distributions of projectile fragmentation products have been simulated by a modified statistical abrasion–ablation model and the isoscaling behaviour of projectile-like fragments has been discussed. The isoscaling parameters α and β have been extracted respectively, for hot fragments before evaporation and cold fragments after evaporation. It looks that the evaporation has stronger effect on α than β. For cold fragments, a monotonic increase of α and |β| with the increase of Z and N is observed. The relation between isoscaling parameter and the change of isospin content is discussed.

Isoscaling Behaviour in the Isospin-Dependent Quantum Molecular Dynamics Model

The isoscaling behaviour is investigated in a frame of isospin-dependent quantum molecular dynamics models. The isotopic yields ratio Y2/Y1 for reactions 48Ca+48Ca and 40Ca+40Ca at different entrance channels are simulated and presented, the relationship between the isoscaling parameter and the entrance channel is analysed, the results show that α and β reduce with the rise of incident energies and increase with the impact parameter b, which can be attributed to the temperature varying of the pre-fragments in different entrance channels. The relation of α and symmetry-term coefficient Csym reveals that the chemical potential difference Δμ is sensitive to the symmetry-term coefficient Csym, and raises with the increasing Csym.

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.

One-Proton Halo Structure in 23Al

The Glauber theory is used to investigate the reaction cross section of proton-rich nucleus 23Al. A core plus a proton structure is assumed for 23Al. HO-type density distribution is used for the core while the density distribution for the valence proton is calculated by solving the eigenvalue problem of Woods–Saxon potential. The transparency function in an analytical expression is obtained by adopting multi-Gaussian expansion for the density distribution. Coulomb correction and finite-range interaction are introduced. This modified Glauber model is suitable for halo nuclei. A dominate s-wave is suggested for the last proton in 23Al from our analysis which is possible in the calculation of relativistic mean-field theory.

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.

Isoscaling of the fission fragments with Langevin equation

The Langevin equation is used to simulate the fission process of 112Sn + 112Sn and 116Sn + 116Sn. The mass distribution of the fission fragments are given by assuming the process of symmetric fission or asymmetric fission with the Gaussian probability sampling. The isoscaling behaviour has been observed from the analysis of fission fragments of both the reactions, and the isoscaling parameter α seems to be sensitive to the width of fission probability and the beam energy.

Investigation on the deformation of Ne and Mg isotope chains within relativistic mean-field model

Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field (RMF) model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that 19,29,32Ne and 20,31Mg maybe have a triaxial deformation and 25−28Ne and 27−30Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for 20Mg is predicted to be very weak.

Investigation of exotic structure of the largely deformed nucleus Al-23 in the relativistic-mean-field model

A candidate for proton halo nucleus 23Al is investigated based on the constrained calculations in the framework of the deformed relativistic mean field (RMF) model with the NL075 parameter set. It is shown by the constrained calculations that the ground state of 23Al has a large deformation that corresponds to the prolate shape. With that large deformation, the non-constrained RMF calculation predicts that there appears an inversion between the 2s1/2 [211] and 1d5/2 [202] shells. The valence proton of 23Al is weakly bound and occupies 2s1/2 [211] and 1d5/2 [202] with the weights of 56% and 29%, respectively. The calculated RMS radius for matter is in agreement with the experimental one. It is also predicted that the difference between the proton RMS radius and the neutron one is very large. This suggests that there exists a proton halo in 23Al.

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.