Showing papers by "Jie Meng published in 2007"

Shell Structure and $ρ$-Tensor Correlations in Density-Dependent Relativistic Hartree-Fock theory

Abstract: A new effective interaction PKA1 with \ensuremath{\rho}-tensor couplings for the density dependent relativistic Hartree-Fock (DDRHF) theory is presented. It is obtained by fitting selected empirical ground state and shell structure properties. It provides satisfactory descriptions of nuclear matter and the ground state properties of finite nuclei at the same quantitative level as recent DDRHF and relativistic mean field (RMF) models. Significant improvement in the single-particle spectra is also found due to the inclusion of \ensuremath{\rho}-tensor couplings. As a result, PKA1 cures a common disease of the existing DDRHF and RMF Lagrangians, namely, the artificial shells at 58 and 92, and recovers the realistic subshell closure at 64. Moreover, the proper spin-orbit splittings and well-conserved pseudospin symmetry are obtained with the new effective interaction PKA1. Due to the extra binding introduced by the \ensuremath{\rho}-tensor correlations, the balance between the nuclear attractions and the repulsions is changed, and this constitutes the physical reason for the improvement of the nuclear shell structure.

Chiral bands for a quasi-proton and quasi-neutron coupled with a triaxial rotor

Abstract: A particle rotor model (PRM) with a quasi-proton and a quasi-neutron coupled with a triaxial rotor is developed and applied to study chiral doublet bands with configurations of an ${h}_{11/2}$ proton and an ${h}_{11/2}$ quasi-neutron. With pairing treated by the BCS approximation, the present quasiparticle PRM is aimed at simulating one proton and many neutron holes coupled with a triaxial rotor. After a detailed analysis of the angular momentum orientations, energy separation between the partner bands, and behavior of electromagnetic transitions, for the first time we find aplanar rotation or equivalently chiral geometry beyond the usual one proton and one neutron hole coupled with a triaxial rotor.

Neutron skin deduced from antiprotonic atom data

Abstract: The relationship between the nucleon density at large radii and the value of the rms radius is investigated in the framework of Skyrme Hartree-Fock and relativistic mean-field models. From a comparison to the charge density we constrain the models in terms of the nuclear matter incompressibility and effective mass properties required to reproduce the density shape. The results are used to extract the rms neutron radius for $^{208}\mathrm{Pb}$ from antiprotonic atom data. The result for the difference between the neutron and proton rms radii, the so-called neutron-skin thickness, is $S=0.20(\ifmmode\pm\else\textpm\fi{}0.04)(\ifmmode\pm\else\textpm\fi{}0.05)$ fm, where $\ifmmode\pm\else\textpm\fi{}0.04$ fm is experimental error from the antiprotonic line width, and $\ifmmode\pm\else\textpm\fi{}0.05$ fm is the theoretical error suggested from the comparison of the models with the experimental charge density.

Doublet bands in Cs-126 in the triaxial rotor model coupled with two quasiparticles

Abstract: The positive-parity doublet bands based on the pi h(11/2)circle times nu h(11/2) configuration in Cs-126 were investigated in the two quasiparticles coupled with a triaxial rotor model. The energy spectra E(I), energy staggering parameter S(I)=[E(I)-E(I-1)]/2I,B(M1) and B(E2) values, intraband B(M1)/B(E2) ratios, B(M1)(in)/B(M1)(out) ratios, and orientation of the angular momentum for the rotor as well as the valence proton and neutron are calculated. After including the pairing correlation, good agreement has been obtained between the calculated results and the data available, which supports the interpretation of this positive-parity doublet bands as chiral bands.

Discovery of a new long-lived isomeric state in 125Ce

Abstract: A new long-lived isomeric state in the near proton dripline nucleus 125Ce has been identified with Schottky mass spectrometry at GSI. The excitation energy E * = 103(12)keV and the decay time of 193(1)s have been obtained from a single stored fully ionized 125m Ce58+ ion. The data implies an E3 transition and a 1/2+ assignment for the spin of the isomer.

Examining the chiral geometry in 104Rh and 106Rh

Abstract: The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Two representative cases in $A\sim100$ odd-odd nuclei, nearly degenerate $\Delta I =1$ doublet bands in $^{104}$Rh and $^{106}$Rh are checked against these chiral criteria. It is shown that $^{106}$Rh possesses better chiral geometry than $^{104}$Rh, although the energy near degeneracy is achieved in $^{104}$Rh in comparison with the constant energy separation of doublet bands in $^{106}$Rh.

Relativistic wave functions for single-proton resonant states

Abstract: With the relativistic boundary condition, single-proton resonant states in spherical nuclei are studied by an analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean-field (RMF) theory. In this scheme, we investigate the wave functions for l≠ 0 proton resonant states close to the continuum threshold in the stable nuclide 120Sn for the first time. Some hints for pseudospin symmetry in the resonant states of nuclei are mentioned as well.

Constrained relativistic mean-field approach with fixed configurations

Abstract: A diabatic (configuration-fixed) constrained approach to calculate the potential energy surface (PES) of the nucleus is developed in the relativistic mean-field model. As an example, the potential energy surfaces of 208Pb obtained from both adiabatic and diabatic constrained approaches are investigated and compared. It is shown that the diabatic constrained approach enables one to decompose the segmented PES obtained in usual adiabatic approaches into separate parts uniquely characterized by different configurations, to follow the evolution of single-particle orbits till the very deformed region, and to obtain several well-defined deformed excited states which can hardly be expected from the adiabatic PESs.

Binding energy differences of mirror nuclei in a time-odd triaxial relativistic mean field approach

Abstract: The binding energy differences of mirror nuclei with A=15,17,27,39, and 41 are calculated using a time-odd triaxial relativistic mean field approach with PK1. Compared with the axially deformed RMF calculations with PK1, NL3, and NLSH, the discrepancy between the calculated and experimental values, i.e., Okamoto-Nolen-Schiffer (ONS) anomaly, is systematically reduced by the appropriate treatment of the gamma deformation degree of freedom, center-of-mass motion, and core polarization effect.

Structure of nuclei far from the stability in relativistic approach

Abstract: The recent progress of the relativistic many-body approach by the group at Peking University will be reviewed. In particular, axially deformed relativistic Hartree-Bogoliubov approach in Woods-Saxon basis aiming at halo nucleus, time-odd triaxial RMF approach, the adiabatic and configuration-fixed constrained triaxial RMF approaches, a Reflection ASymmetric RMF (RAS-RMF) approach, and a new relativistic Hartree-Fock (RHF) approach with density-dependent σ,ω,ρ and π meson-nucleon couplings for finite nuclei and nuclear matter, will be highlighted.