Nuclear Structure in China 2012

The following sections are included:

• PREFACE

• CONTENTS

Effects of the tensor force on the Gamow-Teller (GT) and Charge-exchange Spin-Dipole (SD) transitions in ²⁰⁸Pb and ⁹⁰Zr are studied through self-consistent Hartree-Fock plus Random-Phase-Approximation (HF₊RPA) theory based on Skyrme force. It is found that tensor force produce strong effect on the GT and SD transitions. These strong effects can be good candidates to constrain the strength of tensor force or choose Skyrme parameter sets which included the tensor force.

With the uranium and plutonium isotopes as target materials, we have calculated the formation cross sections of a new superveavy nuclide ²⁷²Ds via the hot fusion reactions ³²S + ²⁴⁴Pu, ³⁴S + ²⁴²Pu, ³⁸Ar + ²³⁸U and ⁴⁰Ar + ²³⁵U. Among these reactions, ²⁴²Pu(³⁴S,4n)²⁷²Ds is the most favorable one with maximum evaporation residue (ER) cross section of 9 pb. Although mass asymmetry of the projectile-target combination ³²S + ²⁴⁴Pu is somehow larger than that of system ³⁴S + ²⁴²Pu, the maximum ER cross section of the former one is two orders of magnitude smaller than that of the later case. By means of a detail analysis, it is found that the different Q-values of these two reactions bring about this dramatic difference in the formation cross sections. The maximum cross sections of ²³⁵U(⁴⁰Ar,3n)²⁷²Ds and ²³⁸U(³⁸Ar,4n)²⁷²Ds fusion-evaporation reactions are about 7 and 2 pb respectively. The larger cross section of ²³⁵U(⁴⁰Ar,3n)²⁷²Ds is mainly due to the larger survival probability of the excited compound nucleus ²⁷⁵Ds in the 3n evaporation channel.

Binding energies and even-odd mass differences of rare-earth ^160–170Er nuclei are calculated by using the exactly solvable mean-filed plus nearest-orbit pairing model and compared with the corresponding experimental values. And the ground state occupation probabilities of valence nucleon pairs with definite angular momentum quantum number for ^{160, 162, 164}Er in the model fitted are calculated. The analysis shows that the ground state occupation probabilities with even angular momenta are much larger than those with odd angular momenta. The results clearly indicate that S, D, and G valence nucleon pairs dominate in the ground state of these nuclei.

We systematically calculate the spontaneous fission half-lives for heavy and spuerheavy nuclei between U and Z=114. The spontaneous fission process is treated as a semi empirical WKB framework. The potential barrier is obtained by a generalized liquid drop model(GLDM), taking into account the nuclear proximity, the mass asymmetry, the accurate nuclear radius, and the microscopic shell correction. Macroscopic inertial-mass functions has been employed for the calculation of the fission half-lives. The results reproduce experimental data rather well.

The recent experimental results on the isoscalar giant monopole resonance (ISGMR) and the Pygmy dipole resonance (PDR) inspire us to explore the nuclear equation of state (EOS) from those new results. We have studied the ISGMR in Cd and Sn isotopes within the self-consistent Skyrme HF₊BCS and quasi-particle random phase approximation (QRPA) and shown some interesting results. The correlations between the behavior of the nuclear symmetry energy, and the percentage of energy-weighted sum rule (EWSR) exhausted by the PDR in ⁶⁸Ni and ¹³²Sn are investigated within RPA approach by using different Skyrme models. A comparison with the experimental data has allowed us to constrain the value of the slope of the symmetry energy at saturation.

The _{pp → p}ΛK⁺ and _{pp → p}Σ⁰K⁺ reactions near threshold are studied using the chiral unitary model. The single-pion and single-kaon exchanges are taken into account as well as the final state interactions of nucleon-hyperon, K-hyperon and K-nucleon systems. We calculate the total cross section of the _{pp → p}ΛK⁺ reaction which is consistent with the experimental data. We also calculate the total cross section of the _{pp → p}Σ⁰K⁺ reaction. Our result can explain the experimental observed strong suppression of Σ⁰ production compared to Λ production at the same excess energy.

We summarize the current status on constraining the density dependence of the symmetry energy from terrestrial laboratory measurements and astrophysical observations. While the value Esym(ρ0) and density slope L of the symmetry energy at saturation density ρ0 can vary largely depending on the data or methods, all the existing constraints are essentially consistent with Esym(ρ0) = 31 ± 2 MeV and L = 50 ± 20 MeV. The determination of the supra-saturation density behavior of the symmetry energy remains a big challenge.

The occurrence of parity doublets is a manifestation of intrinsic reflection asym-metry in odd-A nuclei. The reflection asymmetric shell model calculations of the parity doublet high spin bands have been performed for ²³⁷U and ²³⁹Pu. With a proper octupole deformation the present calculations have well reproduced the experimental data for the K = 1/2 parity doublets. The parity splitting at the lowest spin and its quenching with increasing spin are all re-produced by the theory. The K = 5/2 and K = 7/2 parity doublets have been predicted by the calculations to occur as the low energy bands.

The Heavy Shell Model (HSM) is introduced as an extended Projected Shell Model (PSM), which combines the advantages of two existing models, the PSM and the Fermion Dynamical Symmetry Model (FDSM). As a First numerical realization of the HSM, the energy scheme and B(E2) values of ²³⁴U are reproduced and agree with observed experimental data quite well. Some predicted low-lying bands have not yet been measured, remaining to be tested experimentally.

Rotational structure and observed long bands in ¹²⁵Xe are investigated with the configuration-dependent cranked Nilsson-Strutinsky approach. The observed long bands, especially the unconnected long bands are compared with the calculated configuration assigned to the band and the agreement between experiment and theory at high spin is remarkable. The observed long bands are confirmed as highly deformed and their properties are explained theoretically. There is shape coexistence within the same configuration from low spin to intermediate spin. Possible normal deformed bands with rotation around the intermediate principal axis in several interesting configurations of ¹²⁵Xe are discussed. The calculated results indicate ¹²⁵Xe is near prolate at high spin with large deformation of ε₂ ∼0.36, and may rotate around the intermediate principal axis at low spin with ε₂ ∼0.20 and γ ∼ −40°.

High-spin states of ^{194, 195}Au, ¹⁹⁵Pt and ¹⁹³Ir have been studied using an in-beam γ-ray spectroscopic technique following the reaction of ⁷Li on an ¹⁹²Os target at 44 MeV. The emitted γ rays were observed using an array of 14 Compton-suppressed HPGe detectors. Several bands in these nuclei have been identified and extended up to high-spin states. The α and t emission channels leading to ¹⁹³Ir and ¹⁹⁵Pt, respectively, are strongly enhanced which may be explained by incomplete fusion reaction; the t and α fragments from the break-up of weakly bound ⁷Li nucleus fusion with ¹⁹²Os target.

The low-lying states in ¹⁶⁶Er are analyzed within a current implementation for beyond the relativistic mean-field approximation, namely the five-dimensional collective Hamiltonian determined by a constrained triaxial relativistic mean-field calculations. The results are in good agreement with the data, except the missing of two low-energy excited 0⁺ states. This points out one limitation of current implementation of collective Hamiltonian for the nuclear low-energy excitations.

We report on some recent developments in our understanding of the light-quark mass dependence and the SU(3) flavor symmetry breaking corrections to the magnetic moments of the ground-state baryons in a covariant formulation of baryon chiral perturbation theory, the so-called EOMS formulation. We show that this covariant ChPT exhibits some promising features compared to its heavy-baryon and infrared counterparts.

The high spin states of ¹⁰⁶Pd have been investigated with in-beam γ-ray spectroscopic methods using the ¹⁰⁰Mo(¹¹B, 1_p4n)¹⁰⁶Pd reaction at a beam energy 60 MeV. All earlier known bands were extended considerably and additional bands were identified. On the basis of the experimental aligned angular momenta and the TRS calculations, the configurations of these bands were discussed respectively. Both two-quasineutron and two-quasiproton structures have been found in ¹⁰⁶Pd. The non-yrast low-lying positive-parity band was interpreted as γ-vibrational band.

X-_γ-ray coincidence measurement is a good method to obtain cross-sections when the evaporation residues are decaying by electron capture.In this paper, a X-_γ ray coincidence measurement system was established to obtain the absolute fusion cross-section of ¹⁶O₊¹⁸⁶W at energies around the Coulomb barrier. The results indicate that this method can efficiently decline the background and the cross-sections extracted from our job are in accord with ones measured by using recoil mass separator.

A new _γ-detector array at Institute of modern physics in Lanzhou is now in construction. The spherical frame is designed using Solidworks, and is assembled by 4 kinds of irregular polygons. 32 detectors could be placed on this frame in maximum, which are arranged with 4-4-4-8-4-4-4 configuration.

Every kinds of cluster radioactivities have different radioactive features depending on their emitted clusters and daughters nuclei. Thus each decay process can be treated as a radioactive channel, and the channels can be coupled to each other. Therefore some channels are abated or strengthen due to the coupling effects. Here we attempt to find out a way to evaluate the influence of each channel, and then introduce a physical quantity M_i to express this effect.

The nucleon-nucleon interactions in finite nucleus are systematically investigated within the density-dependent relativistic Hartree-Fock (DDRHF) theory by taking ¹³²Sn as the representative. It is found that the neutron-neutron interactions in ¹³²Sn represent strong spin dependence, and such strong spin dependence is mainly determined by the Fock contributions in the isoscalar channels, i.e., the σ- and ω- couplings, which indicates that there may exist distinct tensor effects in the isoscalar channels as well as the isovector (ρ- and π) ones.

We discuss the influence of the symmetry energy on the properties of super-heavy nuclei and hyperonization in asymmetric matter. On the hand, the role of the hyperonization in shifting the symmetry energy is also discussed preliminarily.

In order to extract the symmetry energy, the Z_bound (the sum of charge number for fragments having Z ≥ 2) dependence of multiplicity of neutrons (M_n) from the projectile spectator fragmentation of ¹²⁴Sn and ¹²⁴La at 600 MeV/nucleon within isospin quantum molecular dynamics (IQMD) model is compared with the experimental findings of ALADIN2000 collaboration.¹² The findings favor the soft symmetry energy with soft equation of state. For all the projectiles (¹²⁴Sn, ¹²⁴ La, ¹⁰⁷ Sn), the peak M_n obey the universal behavior around Z_bound/Z_Projectile ≈ 0.7 with different value of M_n ≈ 12, 9, 7, respectively.

The performance of new LaBr₃(Ce) crystals for γ-ray detectors provides a new method for measurements the lifetimes of nuclear states in the sub-nanosecond domain. Especially the decay scheme is rather complex, it is possible to perform precise measurements because of the superior energy resolution and excellent time resolution of the LaBr₃(Ce) detectors, compared to that of BaF₂ scintillators. Two measurements are presented to illustrate the method: one off-line test of the known lifetime of the state in ¹⁵²Eu, another in-beam re-determination of the lifetime of the state in ¹⁷⁴Os.

The high-spin states in the odd-A ⁸⁷Sr were populated by fusion-evaporation reaction ⁸²Se(⁹Be, 4n)⁸⁷Sr at a beam energy of 46 MeV. The positive-parity band for ⁸⁷Sr is extended up to about 7.4 MeV excitation energy and spin values around 31/2ħ in the addition of 39 new transitions. The possible condfigurations of the positive parity band are suggested by comparison with the isotope ⁸⁵Sr and the alignment value of experiment.

Within the density-dependent relativistic Hartree-Fock-Bogoliubov theory, the structure properties of superheavy nuclei are systematically investigated and Z = 120 (N = 184) is predicted as the next proton (neutron) magic number. The emergences of proton and neutron magic shells are found to be essentially related with the broken and restoration of pseudo-spin symmetry, respectively. It is also found that the nodal effects play a substantial role in determining the systematics of shell quenching and enhancement.

Excited states of the odd-odd ¹²⁰I have been investigated via the ¹¹⁰Pd(¹⁴N; 4n), ¹¹⁴Cd(¹⁰B; 4n) and ¹¹⁴Cd(¹¹B; 5n) reactions at beam energies of 64, 48 and 70 MeV, respectively. The previously known bands are extended, and several new bands have been established. The yrast band is extended up to a state which corresponds to the full alignment of all the valance nucleons outside the semi-closed shell. A newly established band is proposed to be the chiral partner of the previously known band.

Two-pion Hanbury-Brown-Twiss (HBT) correlations for central Pb-Pb collisions at the Large-Hadron-Collider (LHC) energy of are investigated with the cascade mode of the microscopic transport model UrQMD (Ultra-relativistic Quantum Molecular Dynamics). The transverse momentum dependence of the HBT radii is extracted from a three dimensional Gaussian fit to the correlator in the longitudinal co-moving system (LCMS). Qualitative agreement with the ALICE data is obtained, however R_out is overpredicted by nearly 50%. The LHC results are also compared to data from the STAR experiment at RHIC. For both energies we find that the calculated R_O/R_S ratio is always larger than data, indicating that the emission in the model is less explosive than observed in the data.

Nuclear charge-exchange spin-dipole (SD) excitations have attracted more and more attention due to their connections with many important issues in nuclear physics, particle physics and astrophysics. In this report, a fully self-consistent description of the fine structure of the SD excitations in ¹⁶O is discussed in the framework of covariant density functional theory with the most up-to-date data. It is found that not only the general profiles but also the details of the J^π = 0⁻, 1⁻, and 2⁻ excitations are well reproduced.

High spins states in ⁸⁶Sr were populated by the reaction ⁸²Se (⁹Be, 5n) ⁸⁶Sr. γ - γ coincidence measurements along with investigation of directional correlation ratios(DCO) were utilized to establish the extended level scheme of ⁸⁶Sr from 13ħ up to 20ħ. Twenty-nine new transitions were found in ⁸⁶Sr. The configurations of ⁸⁶Sr were generally specified tentatively by comparing neighboring nuclei systematically.

To understand the structure of neutron-rich nuclei and to validate the existing theoretical model for the exotic mass region, we study the deformed effect of strongly-deformed, neutron-rich even-even Zr isotopes with neutron number 62 − 66 by implementing the (triaxial)projected shell model. The variation in moments of inertia at low-spin region is analyzed.

Elastic scattering of ⁶He on both proton and carbon targets were measured at 82.3 MeV/nucleon. For both targets, the measured differential cross sections show a large enhancement at small angles relative to the Rutherford cross section, similar to those observed at lower energies for the scattering of halo nuclei. For the proton target, the experimental results were well reproduced by optical model calculations by using the global potential KD02 with a reduction of the real part, as well as by using the microscopic JLM potential with a reduction of imaginary part. For the carbon target, the overall structure of the cross section is reasonably reproduced by the optical model calculations.

Within the density-dependent relativistic Hartree-Fock-Bogoliubov (DDRHFB) theory, the structure properties of Carbon isotopes are systematically studied, by taking the finite-range Gogny D1S with prefix factor 1.1 as the pairing force. The self-consistent DDRHFB calculations indicate the single neutron halo structures in both ¹⁷C and ¹⁹C. It is also found that close to the neutron drip line there exists distinct odd-even staggering on neutron radii, which is tightly related with the block effect.

The proton pygmy dipole resonances (PDRs) in the proton rich nuclei ^17,18Ne are predicted with the interacting shell model. The properties of these PDRs are revealed by the radial transition densities and components of transition matrix. Comparative study on the pygmy and giant dipole resonance are carried out in the same framework. It is shown that the PDR in ¹⁷Ne is highly collective and due to the oscillation of the valence protons against the interior core, while in ¹⁸Ne the dipole resonance in the PDR region is noncollective and more likely to be the configuration splitting of the giant dipole resonance.

The fine structure in the α decay of neutron-deficient Ds, Cn, and 114 isotopes have been systematically predicted using the multi-channel cluster model (MCCM). The theoretical α-decay energy Q_α is deduced from the local formula of Q_α values for heavy and superheavy nuclei. The ground-state rotational states in a daughter nucleus are established based on the macroscopic- microscopic model with some improved ingredients. Exact five-channels microscopic calculations are performed, and the branching ratios to various daughter states and total α-decay half-lives are evaluated. Any adjustable parameter is not introduced in our calculations. It is expected that the present coupled- channel predictions would provide a reference for future structure researches of superheavy nuclei.

Gamow-Teller transitions and stellar electron-capture rates in hot nuclei are computed using the self-consistent finite-temperature relativistic random-phase approximation (FTRRPA). The predicted electron-capture rates in stellar environment for ^54,56Fe are consistent with those obtained in the shellmodel approach. The FTRRPA provides an efficient and accurate theoretical framework for large-scale calculations of stellar electron-capture rates.

The magnetic effects on π⁻/π⁺ ratio as a function of rapidity are investigated. It is found that the π⁻/π⁺ ratio as a function of rapidity significantly altered by the magnetic field created in heavy ion collisions. At beam energies above about 1 GeV/nucleon, while the integrated ratio of total π⁻ to π⁺ multiplicities is not, the differential π⁻/π⁺ ratio is sensitive to the density dependence of nuclear symmetry energy E_sym(ρ). Our findings suggest that magnetic effects should be carefully considered in future studies of using the differential π⁻/π⁺ ratio as a probe of the E_sym(ρ) at supra-saturation densities.

We report on a recent study of finite-volume effects on the lowest-lying octet baryon masses using the covariant baryon chiral perturbation theory up to next-to-leading order by analysing the latest n_f = 2 + 1 lattice QCD results from the NPLQCD Collaboration.

Two-step model is adopted to analyze the fusion process of heavy ion reactions ⁴⁸Ca+²⁵²Es. Based on this model, the fusion is divided into two consecutive steps, i.e., the sticking step and the formation step, and corresponding sticking probability and formation probability are calculated. Combining the statistical evaporation model for the evaporation stage, the maximum residue cross section is 0.23 pb at 3_n, E_lab=252.4 MeV.

Total-Routhian-surface calculations by means of the pairing-deformation-frequency self-consistent cranked shell model have been carried out for germanium and selenium isotopes, in order to search for possible stable triaxial deformations of nuclear states. The triaxiality of |γ| ≈ 30°. for the ground and collective rotational states, that is the limit of the maximum triaxiality, is found in ^64,74Ge. The maximum triaxiality has its origin in a triaxial shell gap at Z = 32.

Based on the relativistic Hartree-Bogoliubov theory, the influence of the effective interactions in the particle-hole channel on the di-neutron correlations is studied in the nuclear matter. In addition, the evolution of several characteristic quantities of di-neutron correlations, namely, the normal and anomalous density distribution functions as well as the probability density of the neutron Cooper pairs, with the neutron Fermi momentum is discussed.

The nucleon-nucleon interaction is investigated by using the ImQMD model with the three sets of parameters IQ1, IQ2 and IQ3 in which the corresponding incompressibility coefficients of nuclear matter are different. Fusion excitation function and the charge distribution of fragments are calculated for reaction systems ⁴⁰Ca+⁴⁰Ca at different incident energies. It is found that obvious differences in the charge distribution were observed at the energy region 10-25A MeV by adopting the three sets of parameters, while the results were close to each other at energy region of 30-45A MeV for the reaction system. It indicates that the Fermi energy region is a sensitive energy region to explore the N-N interaction. The fragment multiplicity spectrum for ²³⁸U+¹⁹⁷Au at 15A MeV are reproduced by the ImQMD model with the set of parameter IQ3. It is concluded that charge distribution of the fragments and the fragment multiplicity spectrum are good observables for studying N-N interaction, and IQ3 is a suitable set of parameters for the ImQMD model.

Octupole instabilities in even-even nuclei near nucleus have been investigated by means of improved total-Routhian-surface calculations with the inclusion of reflection-asymmetric deformations. It is found that the shape evolutions of mirror nuclei are similar between Z = 56 isotopes and N = 56 isotones in the ground-states. As an example, , which has reflection-symmetric shape at low spins, is predicted to be octupole deformed at certain high rotational frequencies. The prediction is confirmed by experiment.

The lifetime knowledge of a nuclear state provides the essential information on transition probabilities for comparison with theoretical nuclear models. A well-known method for picosecond lifetime measurements of excited nuclear states is Recoil Distance Doppler Shift (RDDS) method. Correspondingly a new plunger based on this technique has been developing in CIAE. We use CAD software and Labview to finish the plunger model design and develop a closed control software. A series of methods such as capacitance method, new skills to flatten the foils etc. are applied in building this plunger. Some tests and the latest results with motion and finite element analysis simulations are discussed in this report.

The neutron and proton odd-even mass staggering (OES) are systematically studied within the density-dependent relativistic Hartree-Fock-Bogoliubov (DDRHFB) theory and the density-dependent relativistic Hartree-Bogoliubov (DDRHB) theory. In terms of the finite-range Gogny D1S as the pairing force, both DDRHFB and DDRHB theories can well reproduce the experimental OES, including C, O, Ca, Ni, Zr, Sn, Ce, Gd and Pb isotopes, and N = 50 and 82 isotones. In addition, the optimizations on the pairing force with the prefix factors bring systematical improvements on the OES for the light and heavy nuclei. It is also found that the pairing effects are essentially related with the appropriate description of the nuclear structures, in which the ρ-tensor correlations play an important role.

The fusion mechanism and the production cross sections for the synthesis of superheavy nuclei are studied with the di-nuclear system model with a dynamical potential energy surface (DNS-DyPES model). The potential energy surface is calculated and the fusion probability as a function of angular momentum is also investigated. It is found the fusion probability decreases with increasing the angular momentum. By multiplying the capture cross section, fusion probability and survival probability, the production cross sections for some superheavy nuclei are obtained. It is found the theoretical results are in good agreement with the experimental results.

Excited states of ⁸⁰Br have been investigated via the ⁷⁶Ge(¹¹B, α3n) reaction and a new ΔI = 1 band has been identified which resides ∼ 400 keV above the yrast band. Based on the experimental results, a chiral character of the two bands within the π_g9/2 ⊗ νg_9/2 configuration is proposed, which provides the first evidence for chirality in the A ∼ 80 mass region.

Using an updated Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the balance energies of free protons, free neutrons, and Z=1 particles (including free protons, deuterons and tritons) from mass symmetric heavy-ion collisions with isobars (A=132) are studied. We investigated the initial isospin and nuclear symmetry energy effects on the balance energy, and found that the balance energies of free neutrons and Z=1 particles are influenced by these effects, while the balance energy of free protons is not.

The nuclear magnetic moment is one of the hot topics in nuclear physics. In this report, the relativistic description of the magnetic moment of ¹³³Sb is discussed in the framework of the covariant density functional theory. It is found that, based on the mean field result, the time-odd fields, meson exchange current, and configuration mixing provide substantial corrections, and the total value is in agreement with the experimental data.

The high-spin states in the odd-odd nucleus ⁷⁴As were studied via heavy ion fusion evaporation reaction ⁷⁰Zn(⁷Li, 3n)⁷⁴As at a bombarding energy of 30 MeV. A level scheme with 43 new γ transitions and 28 new levels has been established. Signature inversion has been observed in the yrast bands. And the mechanism of signature inversion has been explained within the framework of two quasiparticles plus rotor model.

The study of shape coexistence in ⁹⁸Sr and ¹⁰⁰Zr within a covariant density functional theory is reported. The mean-field results of energy surface in ß-γ plane and the underlying single-particle structure, together with the beyond mean-field results of excitation energy of state and the electric monopole transition strength determined from the solution of a five-dimensional collective Hamiltonian are discussed.

Based on the (n, γ) ⇌ (γ, n) equilibrium, the neutron density and temperature conditions required for the r-process are constrained with updated nuclear masses. It is found that the uncertainty of determined neutron density and temperature ranges can be greatly minimized when mass values tabulated in the latest Atomic Mass Evaluation AME2011-preview are employed.

We present the production of light (anti)nuclei, (anti)hypertriton and di-Lambda based on coalescence model in central Au+Au collisions at 200GeV. The invariant yields of obtained is found to be consistent with the STAR measurements.¹⁻⁵ The _pT integrated yields for di-Lambda dN_ΛΛ/dy ∼ 2:23×¹⁻⁵, and is not strongly dependent on the parameter employed for coalescence process. Relative particle ratios of light anti(nuclei) and (anti)hypertriton are explored, and agree with experimental data and thermal model predictions⁴⁻⁷ quite well. An exponential reduction behavior is presented for the differential invariant yields with increased baryon number. The production rate reduces by a factor of 1692 (1285) for each additional antinucleon (nucleon) added to antinuclei (nuclei), and the production rate of is predicted to be 10⁻¹⁶ which is consistent with STAR result.

The excited states in ¹⁰⁷Ag were populated through the heavy-ion fusion-evaporation reaction ¹⁰⁰Mo (¹¹B, 4n) ¹⁰⁷Ag at a beam energy of 46 MeV. 12 Compton suppressed HPGe detectors and 2 planar HPGe detectors were employed to detect the de-excited γ rays from the reaction residues. Lifetimes of high spin states in ¹⁰⁷Ag have been measured using the Doppler shift attenuation method (DSAM) and the deduced B(M1) and B(E2) transition probabilities have been derived from the measured lifetimes.

The high-spin states of ¹³⁹Pr have been investigated by using ¹²⁴Sn(¹⁹F,4n) reaction at a beam energy of 80 MeV. The level scheme has been expanded with spin up to 45/2 ħ. Four collective band structures are observed. One band is assigned as a decoupled band, two bands are proposed as the oblate bands with γ ∼ -60°., and another band has been suggested as the oblate-triaxial deformation with γ ∼ -90°.

Excited states of the doubly-odd ¹³⁰Cs have been investigated via the ¹²⁴Sn(¹⁰B, 4n) and ¹²⁴Sn(¹¹B, 5n) fusion-evaporation reactions at beam energies of 47 and 58 MeV, respectively. Based on the observation of some new critical linking transitions, the previous spin assignment for the πh_11/2 ⊗ν_h11/2 band is firmly confirmed. The excitation energy systematics of πh_11/2 ⊗νh_11/2 yrast bands of odd-odd isotopes ^118−132Cs is reinvestigated. Discrepancy between the spin assignments for ^120,122Cs and ¹³⁰Cs is briefly discussed.

The triaxial projected shell model calculation has been performed to investigate the chirality and signature inversion in ¹²⁸Cs. The calculations well reproduce the experimental data for both the chiral doublet bands and the signature inversion. To examine the chiral geometry, the projections of total angular momentum along the three principle axises are calculated. The results do not support the static chirality for the candidate chiral doublets in ¹²⁸Cs.

The quasi-elastic scattering angular distribution of the proton drip line nucleus ¹⁷F on a ¹²C target was measured at 60 MeV. The experimental data have been compared with theoretical analysis based onto optical model and continuum discretized coupled channels (CDCC). The couplings between breakup and elastic scattering channels, and between inelastic and elastic scattering channels resulted weakly.

The ground state properties of Ds (Z = 110) isotopes (N = 151 − 195) are studied in the framework of the relativistic mean field (RMF) theory within the parameters NL-Z2. The pairing correlation is treated within the conventional BCS approximation. The ground properties, especially isotopic shift, competition between α-decay and spontaneous-fission (sf) and single particle spectra are analyzed for Ds isotopes to find new characteristics of superheavy nuclei (SHN). The isotopic shift appears evidently at neutron number N = 184, which is the most impressed result.

The experimental investigation cannot presently distinguish explicitly whether the α particle is preformed in mother nucleus or it is formed during penetrating of the potential barrier. Consequently, the α-decay has been mainly described using the cluster-like theories and the fission-like theories. In any way, the assault frequency plays a pivotal role in the two different decay modes. A microscopic approach is adopted to estimate the assault frequency and the results are consistent with the assault frequency extracted within the cluster-like model, which suggests that the α-decay is rather a radioactive emission process of a cluster preformed in the nucleus but before the potential barrier penetration. The α-decay half-life are estimated in the framework of the preformed cluster-like model to explore the island of stability of superheavy nuclei.

The advanced time delay (ATD) technique, based by delayed coincidence method, and other derived techniques are widely used for short lifetime measurements. This paper presents the principle of the ATD technique, the crucial factors which affect the timing performance of a fast timing setup, and the optimizations of them.

Within the framework of improved Quantum Molecular Dynamics model (ImQMD05), we study three reaction systems, ⁷⁰Zn +⁷⁰ Zn, ⁶⁴Zn +⁶⁴ Zn, ⁶⁴Ni +⁶⁴ Ni at the beam energy of 35 MeV/nucleon at b=4fm. Our study show that that half of the collisions events belong to multi-fragmentation, and another half is binary and ternary fragmentation. The binary events tend to produce more light charged particles (LCPs) at mid-rapidity, and the multi-fragmentation events tend to broaden the rapidity distribution of the yields of LCPs. The experimental results of the reduced rapidity distribution for the yield of p, d, t, ³He, ⁴He and ⁶He at forward rapidity are well reproduced. By comparing the calculated results of to the data, the cumulative evidence on the nuclear symmetry energy at sub-saturation density is obtained.

A scheme that elucidates the nature of critical point symmetries in deformed odd-A nuclei by linking them to critical point symmetries of neighboring even-even nuclei is introduced. Specifically, a new symmetry, called SX(3), is advanced that shows primary characteristics of an assumed strong-coupling limit for odd-A systems.

The recent progress on the self-consistent tilted axis cranking model based on the covariant density functional theory with point-coupling interaction and its application to the antimagnetic rotation (AMR) in nuclei are briefly reported. In particular, the microscopic description of the newly observed AMR band in ¹⁰⁵Cd is discussed. Without any additional parameter, the experimental B(E2) values are reproduced very well. Moreover, the appearance of the “two-shears-like” mechanism in the AMR band is clearly seen.

Excited states in ¹⁰⁶Ag have been studied using the ¹⁰⁰Mo(¹¹B, 5n)¹⁰⁶Ag reaction at the beam energy of 60 MeV. The R_DCO values for the transitions belonging to magnetic rotation band and electric rotation band in ¹⁰⁶Ag show different behavior. The difference of R_DCO values could be regarded as the experimental evidence for the change of rotational axis, which could be explained in the frame of triaxial projected shell model calculation.

In the framework of the Skyrme Hartree-Fock model, we study the effect of hyperons and kaons on nuclear structure. Namely, the structure of hypernuclei is investigated by including into SHF a hyperon-nucleon interaction from microscopic Brueckner-Hartree-Fock calculations of asymmetric nuclear matter. Similarly, we determine the properties of kaonic nuclei in the SHF approach by using the kaon-nucleon interaction from a standard chiral model.

Excited states in ¹²⁶I have been investigated by using in-beam γ-ray spectroscopy with the ¹²⁴Sn(⁷Li, 5n)¹²⁶I reaction at a beam energy of 48 MeV. The yrat band has been extended to the I^π = 22⁻ level, and a new excited band 2 has been observed. The configurations have been tentatively assigned for both bands with the help of triaxial projected shell model and cranked shell model calculations. Some features of chirality are found for the four- quasiparticle (4qp) part of the yrast band and the 4qp excited band 2.

The progress in experimental research on the octupole correlations in neutronrich even-even Ce isotopes by our collaboration has been reviewed. The experiments were carried out by measuring the prompt γ-rays in the spontaneous fission of ²⁵²Cf. The octupole correlations with s = +1 band structure in ^{144, 146, 148, 152}Ce were identified or expanded. The s = ± 1 double octuple band structure in ¹⁴⁸Ce was discovered. Systematic characteristics of the octupole correlations in these even-even Ce isotopes have been discussed.

The following sections are included:

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