Very neutron-deficient nuclei are investigated with Woods-Saxon potentials,especially the newly measured A =2Z-1 nucleus ^(65)As [X.L.Tu et al.,Phys.Rev.Lett.106,112501(2011)],where the experimental proton separation energy is obtained as-90(85) keV for the first time.Careful consideration is given to quasibound protons with outgoing Coulomb wave boundary conditions.The observed proton halos in the first excited state of ^(17)F and in the ground states of ^(26,27,28)P are reproduced well,and predictions of proton halos are made for the ground states of ^(56,57)Cu and ^(65)As.The sensitivity of the results to the proton separation energy is discussed in detail,together with the effect of the l=1 centrifugal barrier on proton halos.
The combination of in-flight fragment separator and the isochronous mass spectrometry(IMS)in storage rings have been proven to be a powerful tool for the precision mass measurements of shortlived exotic nuclei. In IMS, the mass-over-charge ratio is only related to the revolution period of stored ions, and the relative mass resolution can reach up to the order of 10-6. However, the instability of the magnetic field of storage ring deteriorates the resolution of revolution period, making it very difficult to distinguish the ions with very close mass-over-charge ratio via their revolution periods. To improve the resolution of revolution periods, a new method of weighted shift correction(WSC) has been developed to accurately correct the influence of the magnetic field instabilities in the isochronous mass measurements of ^(58)Ni projectile fragments. By using the new method, the influence of unstable magnetic fields can be greatly reduced, and the mass resolution can be improved by a factor up to 1.7. Moreover, for the ions that still cannot be distinguished after correcting the magnetic field instabilities, we developed a new method of pulse height analysis for particle identification. By analyzing the mean pulse amplitude of each ion from the timing detector, the stored ions with close mass-over-charge ratios but different charge states such as ^(34)Ar and ^(51)Co can be identified, and thus the mass of ^(51)Co can be determined. The charge-resolved IMS may be helpful in the future experiments of isochronous mass measurement even for N = Z nuclei.
We investigate low-lying bound states of the neutron-rich nucleus ^(15)B by assuming it is a three-body system made of an inert core 13 B and two valence neutrons. The three-body wave functions are obtained using the Faddeev formalism. Special attention is paid to the excited state at 3.48(6) MeV observed in the 13 C(14 C,12 N)15 B reaction, whose properties are less clear theoretically. In our three-body model, besides the ground state 3/21, a second 3/2_2^-state is discovered at around 3.61 MeV, which might be identified with the excited state observed at3.48(6) MeV. We study this 3/2_2^-state in detail. It turns out to be a two-neutron halo state with a large matter radius r_m≈4.770 fm.
Collective phenomenon in neon isotopes is an interesting topic.However,even the ground-state deformations cannot be well described by theories.Recently,QJ Zhi and ZZ Ren[Phys Lett B 638:166(2006)]have suggested an improved Nilsson potential,which can give a suitable description of ground-state properties in magnesium isotopes.In order to test the description of neon isotopes located around the‘‘island of inversion’’,we have used this potential to provide the deformed basis for the projectedshell-model calculations.The low-lying spectra and transition properties of neon isotopes can be reproduced reasonably.The gyromagnetic factors of neon isotopes have also been investigated.The structures of excited states along the yrast line are studied in the language of band diagrams.
The superheavy nucleus256Rf,where rotational band and multi-quasiparticle isomer have been observed recently,has been investigated using total Routhian surface calculations and configuration-constrained calculations of potential energy surface,with the inclusion of b6deformation.The experimental moment of inertial is well reproduced,indicating that the alignment is delayed due to the b6deformation.A K p=5-or 8-state could form a two-quasiparticle isomer that is calculated to have higher fission barrier than the ground state.
The precise determination of neutron distribution has important implications for both nuclear structure and nuclear astrophysics. The purpose of this paper is to study the characteristics of neutron distribution of^(208) Pb by parity-violating electron scattering(PVS). Parity-violating asymmetries of^(208) Pb with different types of neutron skins are systematically calculated and compared with the experimental data of PREx. The results indicate that the PVS experiments are very sensitive to the nuclear neutron distributions. From further PVS measurements, detailed information on nuclear neutron distributions can be extracted.
β-decay properties of N=18-22,Z=10-14 nuclei are analyzed with a new shell-model Hamiltonian using the Gogny densitydependent interaction.The Gogny force which has been widely and successfully used in mean-field theory can provide reasonable two-body matrix elements for cross-shell calculations.The log f t values andβ-decay level schemes are systematically studied using the D1S-Gogny interaction and compared with the SDPF-M results and experimental data.It is shown that the new Hamiltonian provides reliable results forβ-decay along with subtle level schemes for this region.Shell-model calculations with Gogny interaction can lead to a successful description of nuclei in and around the N=20 island of inversion and supplements experiment where sufficient data are not available.
In the paper we review the recent progress of studies in unstable nuclei,mainly affiliated with the facilities of radioactive ion beams in China,including both experimental and theoretical aspects of researches.Many experiments for reactions,decays and structures have been performed targeting better understandings of properties of unstable nuclei.Special experimental measurements related to nuclear astrophysics have been done to seek insights into the processes of syntheses of elements in the universe.Theoretical calculations have provided many useful predictions on the behaviors of unstable nuclei,with model developments.Studies covered many mass regions from light to superheavy nuclei,giving plenty of information about the structures of unstable nuclei,towards the limits of existence of atomic nuclei.
Pairing-deformation-frequency self-consistent crankingWoods-Saxon model is employed to investigate the triaxiality in the ground states of the neutron-rich even-even Mo, Ru isotopes. Deformation evolutions and transition probabilities have been studied, giving the triaxial shapes in their ground states. The kinematic moments of inertia have been calculated to illustrate the gradually rigid deformation. To understand the origin of the asymmetry shape in this region, we analyze the evolution of single-particle orbits with changing γ deformation. The present calculations reveal the importance of the triaxial deformation in describing not only static property, but also rotational behaviors in this mass region, providing significant probes into the shell structure around.
The influence of short-range correlations in nuclei was investigated with realistic nuclear force. The nucleon-nucleon interaction was renormalized with Vlowk technique and applied to the Green's function calculations. The Dyson equation was reformulated with algebraic diagrammatic constructions. We also analyzed the binding energy of 4He, calculated with chiral potential and CD-Bonn potential. The properties of Green's function with realistic nuclear forces are also discussed.
