The N = 28 shell gap in sulfur, argon, calcium and titanium isotopes is investigated in the framework of relativistic continuum Hartree-Bogoliubov （RCHB） theory. The evolutions of neutron shell gap, separation energy, single particle energy and pairing energy are analyzed, and it is found that the N = 28 shell gap is quenched in sulfur isotopes but persists in argon, calcium and titanium isotopes. The evolution of the N = 28 shell gap in the N = 28 isotonic chain is discussed, and the erosion of the N = 28 shell gap is understood with the evolution of potential with proton number.
Single particles moving in a reflection-asymmetric potential are investigated by solving the Schr6dinger equation of the reflectionasymmetric Nilsson Hamiltonian with the imaginary time method in 3D lattice space and the harmonic oscillator basis expansion method. In the 3D lattice calculation, the l2 divergence problem is avoided by introducing a damping function, and the（l2）N term in the non-spherical case is calculated by introducing an equivalent N-independent operator. The efficiency of these numerical techniques is demonstrated by solving the spherical Nilsson Hamiltonian in 3D lattice space. The evolution of the single-particle levels in a reflection-asvmmetric ootential is obtained and discussed bv the above two numerical methods, and their consistencv is shown in the obtained single-particle energies with the differences smaller than 10-4[hω0]
The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with πh11/2×γh11/2^-1.The energy spectra,electromagnetic transition probabilities B（M1） and B（E2）,angular momenta,and K-distributions are studied.It is demonstrated that the chirality still remains not only in the yrast and yrare bands,but also in the two higher excited bands whenγ deviates from 30°.The chiral geometry relies significantly on γ,and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands.
The α-decay energies （Qα） are systematically investigated with the nuclear masses for 10 ≤Z ≤120 isotopes obtained by the relativistic continuum Hartree-Bogoliubov （RCHB） theory with the covariant density func- tional PC-PK1, and compared with available experimental values. It is found that the α-decay energies deduced from the RCHB results present a similar pattern to those from available experiments. Owing to the large predicted Qα values （≥4 MeV）, many undiscovered heavy nuclei in the proton-rich side and super-heavy nuclei may have large possibilities for α-decay. The influence of nuclear shell structure on α-decay energies is also analysed.
The spectroscopic properties and angular momentum geometry of the wobbling motion of a simple triaxial rotor are investigated within the triaxial rotor model. The obtained exact solutions of energy spectra and reduced quadrupole transition probabilities are compared to the approximate analytic solutions from the harmonic approximation formula and Holstein-Primakoff formula. It is found that the low lying wobbling bands can be well described by the analytic formulae. The evolution of the angular momentum geometry as well as the K-distribution with respect to the rotation and the wobbling phonon excitation are studied in detail. It is demonstrated that with the increase of the wobbling phonon number, the triaxial rotor changes its wobbling motions along the axis with the largest moment of inertia to the axis with the smallest moment of inertia. In this process, a specific evolutionary track that can be used to depict the motion of a triaxial rotating nucleus is proposed.
Nuclear masses ranging from O to Ti isotopes are systematically investigated with relativistic continuum Hartree-Bogoliubov(RCHB)theory,which can provide a proper treatment of pairing correlations in the presence of the continuum.From O to Ti isotopes,there are 402 nuclei predicted to be bound by the density functional PC-PK1.For the 234 nuclei with mass measured,the root mean square(rms)deviation is 2.23 MeV.It is found that the proton drip-lines predicted with various mass models are roughly the same and basically agree with the observation.The neutron drip-lines predicted,however,are quite diferent.Due to the continuum couplings,the neutron drip-line nuclei predicted are extended further neutron-rich than other mass models.By comparison with finite-range droplet model(FRDM),the neutron drip-line nucleus predicted by RCHB theory has respectively2(O),10(Ne),10(Na),6(Mg),8(Al),6(Si),8(P),6(S),14(K),10(Ca),10(Sc),and 12(Ti)more neutrons.
QU XiaoYingCHEN YingZHANG ShuangQuanZHAO PengWeiSHIN Ik JaeLIM YeunhwanKIM YoungmanMENG Jie
