Chen Yong-Shou

Reflection asymmetric shell model for the description of octupole rotational bands

The reflection asymmetric shell model has been formulated to describe the high spin states of octupole-deformed nuclei. The long-range separable forces of quadrupole, octupole and hexadecapole, as well as monopole and quadrupole pairing, are included in the Hamiltonian. The bases, on which the Hamiltonian is diagonalized, are the eigenstates of angular momentum and parity obtained by projecting the octupole-deformed multi-quasiparticle states onto good angular momentum and good parity. The general features of rotational octupole bands in even-even nuclei can be reproduced by the model and the calculated result is in good agreement with experiment.

Garvey-Kelson Mass Relations and n-p Interaction

Two Garvey-Kelson mass relations are found to be directly related to the n-p interaction. In the case of the same nuclear core, the neutron-proton interaction energy between two neutrons and one proton epsilon (2n-1p) is experimentally found to be close to that between one neutron and two Protons epsilon (1n-2p), which is equivalent to the first Garvey-Kelson mass relation. The sum of epsilon (2n-1p) and epsilon (1n-2p) is close to the n-p interaction energy between two neutrons and two protons epsilon (2n-2p), which leads to the second Garvey Kelson mass relation. An explanation of these two n-p interaction relations is presented. It is shown that both of these mass relations hold more accurately when the core is an even-even core.

The Main Path to C, N, O Elements in Big Bang Nucleosynthesis

The production of C, N, O elements in a standard big bang nucleosynthesis scenario is investigated. Using the up-to-date data of nuclear reactions in BBN, in particular the 8Li (n,γ) 9Li which has been measured in China Institute of Atomic Energy, a full nucleosynthesis network calculation of BBN is carried out. Our calculation results show that the abundance of 12C is increased for an order of magnitude after addition of the reaction chain 8Li(n,γ) 9Li(α,n) 12B(β) 12C, which was neglected in previous studies. We find that this sequence provides the main channel to convert the light elements into C, N, O in standard BBN.

Study of Triaxial Superdeformation in 162Lu

The triaxially superdeformed states in 162Lu are investigated using the three-dimensional total routhian surface calculation, and the deformation parameters and the likely configuration are given. The shell and pairing correction energies are considered respectively, and the formation mechanism of triaxial superdeformation is investigated.

Triaxial superdeformed band and its formation mechanism in odd-odd nucleus Lu-168

Three-dimensional total Routhian surface calculations are carried out to determine the triaxial superdeformation of odd-odd nucleus Lu-168. One of the new four rotational bands observed in the experiment is identified as a triaxial superdeformed band, in which the neutron shell correction energy plays a key role and the deformation-driving effect of high j intruder orbital plays an additional role in the formation of triaxial superdeformation shape. Its deformation parameters (epsilon(2), epsilon(4), gamma) are derived from the analysis, which can reproduce the experimental assignment.

Rotational Band Structures of Non-Axial Octupole Deformed Shapes

The rotational band structures associated with the intrinsic non-axial octupole deformed states, especially for the intrinsic ground state of the even-even nuclei, are analysed by using the reflection asymmetric shell model. These band structures are expected to be useful in identifying such exotic shapes from experiment. As an example, a possible triangular shape Of Sm-148 is suggested.

Theoretical Simulation for Identical Bands

The frequency of occurrence of identical bands is studied by analysing a large number of rotational bands calculated with the reflection asymmetric shell model, and the statistical properties of identical bands indicated in all the experimental observations are reproduced within the mean field approximation and beyond mean field treatment, such as angular momentum projection. The distributions of the calculated J(2), Eγ and the fractional change of J(2) are discussed.

Calculation of Cross Section of Radiative Halo-Neutron Capture by 12C at Stellar Energy with the Asymptotic Normalization Coefficient Method

The cross section of the direct neutron capture reaction C-12(n,gamma)C-13(1/2(+)) is calculated with the asymptotic normalization coefficient method. The result is in good agreement with a recent experiment at low energy. An enormous enhancement of cross section is found for this direct neutron capture in which a p-wave neutron is captured into an 2s(1/2) orbit with neutron halo. The possible effect of the neutron halo structure presented in this reaction on the s-process in astrophysics is. discussed in general.

Band Structures of the Axial and Triaxial Deformed Nuclei in the Reflection Asymmetric Shell Model

Band structures for axial and triaxial deformed nuclei are analysed in the reflection asymmetric shell model. The characteristics of the low-lying rotational spectra corresponding to different nuclear intrinsic shapes are given.

Reflection Asymmetric Shell Model on the Projected Woods-Saxon+BCS Basis

The projected Woods-Saxon (WS) quasi-particle states have been used as the bases in the calculation of the reflection asymmetric shell model (RASM). The WS potential has been modified but constrained to give the similar single-particle levels of the standard WS potential. Correspondingly, the multipole interactions in the total RASM Hamiltonian are constructed according to the modified WS potential. The calculated octupole band of Th-228 from this approach is in good agreement with experimental data.