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The multidimensionally-constrained covariant density functional theories (MDC-CDFTs) have been developed to study the influence of octupole and triaxial deformations on the ground state and fission properties. In this paper, we present a brief review of the applications of MDC-CDFTs and discuss the results of a systematical study of even-[Formula: see text] uranium isotopes with the multidimensionally-constrained relativistic mean field (MDC-RMF) model which is one of the MDC-CDFTs with pairing correlations treated by using the Bardeen-Cooper-Schrieffer (BCS) approach. We examine in detail the two-dimensional potential energy surfaces [Formula: see text] of these U isotopes and discuss the ground state and fission properties as well as the third and fourth minima on the potential energy surfaces. The emphasis is put on the effects of octupole and triaxial deformations.

New effective $\Lambda N$ interactions are proposed for the density dependent relativistic mean field model. The multidimensionally constrained relativistic mean field model is used to calculate ground state properties of eleven known $\Lambda$ hypernuclei with $A\ge 12$ and the corresponding core nuclei. Based on effective $NN$ interactions DD-ME2 and PKDD, the ratios $R_\sigma$ and $R_\omega$ of scalar and vector coupling constants between $\Lambda N$ and $NN$ interactions are determined by fitting calculated $\Lambda$ separation energies to experimental values. We propose six new effective interactions for $\Lambda$ hypernuclei: DD-ME2-Y1, DD-ME2-Y2, DD-ME2-Y3, PKDD-Y1, PKDD-Y2 and PKDD-Y3 with three ways of grouping and including these eleven hypernuclei in the fitting. It is found that the two ratios $R_\sigma$ and $R_\omega$ are correlated well and there holds a good linear relation between them. The statistical errors of the ratio parameters in these effective interactions are analyzed. These new effective interactions are used to study the equation of state of hypernuclear matter and neutron star properties with hyperons., Comment: 11 pages, 4 figures

The angular momentum projection (AMP) method is implemented in the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the point-coupling density functional. The wave functions of angular momentum projected states are expanded in terms of the Dirac Woods-Saxon (WS) basis, providing a proper description of the asymptotic behavior of the wave functions for weakly bound nuclei. The contribution of continuum induced by the pairing is considered by treating the pairing correlation with the Bogoliubov transformation. We present the formulae and numerical checks for the DRHBc+AMP approach and use it to study low-lying excited states of weakly bound deformed nuclei. Our calculations show that neutron-rich magnesium isotopes $^{36,38,40}$Mg are all well deformed nuclei. The low-lying excited states of these three nuclei are obtained by performing the AMP on the mean-field ground-states. The ground-state rotational bands of $^{36,38,40}$Mg are reproduced reasonably well by using this new DRHBc+AMP approach with the density functional PC-F1., 18 pages, 11 figures, 3 tables

A new α-emitting isotope ^{214}U, produced by the fusion-evaporation reaction ^{182}W(^{36}Ar,4n)^{214}U, was identified by employing the gas-filled recoil separator SHANS and the recoil-α correlation technique. More precise α-decay properties of even-even nuclei ^{216,218}U were also measured in the reactions of ^{40}Ar, ^{40}Ca beams with ^{180,182,184}W targets. By combining the experimental data, improved α-decay reduced widths δ^{2} for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N=126 are deduced. Their systematic trends are discussed in terms of the N_{p}N_{n} scheme in order to study the influence of proton-neutron interaction on α decay in this region of nuclei. It is strikingly found that the reduced widths of ^{214,216}U are significantly enhanced by a factor of two as compared with the N_{p}N_{n} systematics for the 84≤Z≤90 and N

We investigate the ground state properties of $^{22}$C by using a deformed relativistic Hartree-Bogoliubov model in continuum and explore the interplays among the formation of a halo, deformation effects, the inversion of $sd$ states, the shell evolution, and changes of nuclear magicities. It is revealed that there is an inversion between the two spherical orbitals $2s_{1/2}$ and $1d_{5/2}$ in $^{22}$C compared with the conventional single particle shell structure in stable nuclei. This inversion, together with deformation effects, results in a shrunk halo and a quenched shell gap at $N=16$. It is predicted that the core of $^{22}$C is oblate but the halo is prolate. Therefore several exotic nuclear phenomena, including the halo, the shape decoupling effects, the inversion of $sd$ states, and the evolution of shell structure which results in (dis)appearance of magic numbers, coexist in one single nucleus $^{22}\mathrm{C}$., Phys. Lett. B, in press

We explore the rotational feature of deformed halos by performing the angular momentum projection (AMP) on the ground state wave functions obtained from the deformed relativistic Hartree-Bogoliubov theory (DRHBc) in continuum. The DRHBc+AMP approach self-consistently describes the coupling between single particle bound states and the continuum not only in the ground state but also in rotational states. The rotational modes of deformed halos in $^{42}$Mg and $^{44}$Mg are investigated by studying properties of rotational states such as excitation energy, configuration, and density distribution. Our study demonstrates that the deformed halo structure persists from the ground state in the intrinsic frame to collective states. Especially, the typical behavior of shape decoupling effects in rotating deformed halo nuclei is revealed., 7 pages, 5 figure, and 1 table

Self-consistent methods for the structure of heavy and superheavy nuclei are reviewed. The construction and application of energy-density functionals are discussed. The relationship between the self-consistent methods and microscopic-macroscopic approaches is considered on the mean-field level. The extraction of single-particle potentials from the energy-density functional is described. The isotopic dependence of nucleon distributions and its influence on the nucleus–nucleus interaction is analyzed. As a new additional condition we introduce that the energy-density functional must describe the heights of the Coulomb barriers in nucleus–nucleus interaction potentials, thus imposing constraints on the properties of the functional at low matter densities. The self-consistent methods are applied to describe the quasiparticle structure, cluster radioactivity, and fission of the heaviest nuclei. These methods are used to predict the probabilities of $$\beta $$ -delayed multi-neutron emission and half-lives of $$\beta $$ -decays and electron captures in heavy and superheavy nuclei. The predicted properties of superheavy nuclei are used to estimate the production cross-sections of superheavy nuclei in complete fusion reactions.

A kinematically complete quasifree (p,pn) experiment in inverse kinematics was performed to study the structure of the Borromean nucleus ^{17}B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for 1s_{1/2} and 0d_{5/2} orbitals, and a surprisingly small percentage of 9(2)% was determined for 1s_{1/2}. Our finding of such a small 1s_{1/2} component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in ^{17}B. The present work gives the smallest s- or p-orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of s or p orbitals is not a prerequisite for the occurrence of a neutron halo.

The effects of the ϕ meson on the properties of hyperon stars are studied systematically in the framework of the density-dependent relativistic mean field (DDRMF) model. The ϕ meson shifts the hyperon threshold to a higher density and reduces the hyperon fractions in neutron star cores. It also strongly stiffens the equation of state calculated with various DDRMF effective interactions and increases the maximum mass of hyperon stars, but only a few effective interactions survive under the constraints from recent astrophysical observations. In the DDRMF model, the conformal limit of the sound velocity is still in strong tension with the fact that the maximum mass of neutron stars obtained in theoretical calculations reaches about 2 M ⊙. Based on different interior composition assumptions, we discuss the possibility of the secondary object of GW190814 as a neutron star. When the ϕ meson is considered, DD-ME2 and DD-MEX support the possibility that the secondary object of GW190814 is a hyperon star rapidly rotating with Kepler frequency.

A new, very short-lived neutron-deficient isotope $^{222}\mathrm{Np}$ was produced in the complete-fusion reaction $^{187}\mathrm{Re}(^{40}\mathrm{Ar},5\mathrm{n})^{222}\mathrm{Np}$, and observed at the gas-filled recoil separator SHANS. The new isotope $^{222}\mathrm{Np}$ was identified by employing a recoil-$\ensuremath{\alpha}$ correlation measurement, and six $\ensuremath{\alpha}$-decay chains were established for it. The decay properties of $^{222}\mathrm{Np}$ with ${E}_{\ensuremath{\alpha}}=10016(33)\text{ }\text{ }\mathrm{keV}$ and ${T}_{1/2}=38{0}_{\ensuremath{-}110}^{+260}\text{ }\text{ }\mathrm{ns}$ were determined experimentally. The $\ensuremath{\alpha}$-decay systematics of Np isotopes is improved by adding the new data for $^{222}\mathrm{Np}$, which validates the $N=126$ shell effect in Np isotopes. The evolution of the $N=126$ shell closure is discussed in the neutron-deficient nuclei up to Np within the framework of $\ensuremath{\alpha}$-decay reduced width.

We investigate the stability and ${e}^{+}{e}^{\ensuremath{-}}$ pair creation of supercritically charged superheavy nuclei, $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets based on the Thomas-Fermi approximation. The model parameters are fixed by reproducing masses and charge properties of these supercritically charged objects reported in earlier publications. It is found that $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets may be more stable than $^{56}\mathrm{Fe}$ at the baryon number $A\ensuremath{\gtrsim}315$, $5\ifmmode\times\else\texttimes\fi{}{10}^{4}$, and $1.2\ifmmode\times\else\texttimes\fi{}{10}^{8}$, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number $\ensuremath{\sim}965$, while $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than 39, 433, and $2.7\ifmmode\times\else\texttimes\fi{}{10}^{5}$. The ${e}^{+}{e}^{\ensuremath{-}}$ pair creation will inevitably start for superheavy nuclei with charge numbers $Z\ensuremath{\ge}177$, for $ud\mathrm{QM}$ nuggets with $Z\ensuremath{\ge}163$, for strangelets with $Z\ensuremath{\ge}192$, and for strangeon nuggets with $Z\ensuremath{\ge}212$. A universal relation $Q/{R}_{e}=({m}_{e}\ensuremath{-}{\overline{\ensuremath{\mu}}}_{e})/\ensuremath{\alpha}$ is obtained at a given electron chemical potential ${\overline{\ensuremath{\mu}}}_{e}$, where $Q$ is the total charge and ${R}_{e}$ the radius of electron cloud. The maximum number of $Q$ without causing ${e}^{+}{e}^{\ensuremath{-}}$ pair creation is then fixed by taking ${\overline{\ensuremath{\mu}}}_{e}=\ensuremath{-}{m}_{e}$. For supercritically charged objects with ${\overline{\ensuremath{\mu}}}_{e}l\ensuremath{-}{m}_{e}$, the decay rate for ${e}^{+}{e}^{\ensuremath{-}}$ pair production is estimated based on the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. It is found that most positrons are emitted at $t\ensuremath{\lesssim}{10}^{\ensuremath{-}15}\text{ }\text{ }\mathrm{s}$, while a long lasting positron emission can be observed for large objects with $R\ensuremath{\gtrsim}1000\text{ }\text{ }\mathrm{fm}$. The emission of positrons and electron-positron annihilation from supercritically charged objects may be partially responsible for the short $\ensuremath{\gamma}$-ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in x-ray spectra from galaxies and galaxy clusters.

The aim of this work is to develop the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) theory based on the point-coupling density functionals and extend it to provide a unified description for all even-even nuclei in the nuclear chart by overcoming all possible challenges. The nuclear superfluidity is considered via Bogoliubov transformation. Densities and potentials are expanded in terms of Legendre polynomials to include the axial deformation degrees of freedom. Sophisticated relativistic Hartree-Bogoliubov equations in coordinate space are solved in the DiracWoods-Saxon basis to consider the continuum effects. Numerical checks are performed from light nuclei to heavy nuclei. The techniques to construct the DRHBc mass table for even-even nuclei are explored. The DRHBc theory is extended to study heavier nuclei beyond magnesium isotopes. Taking Nd isotopes as examples, the experimental binding energies, two-neutron separation energies, quadrupole deformations, and charge radii are reproduced rather well. The deformation and continuum play essential roles in the description of nuclear masses and prediction of drip-line nuclei. By examining the single-particle levels in the canonical basis and their contributions to the total density, the thickness of the neutron skin, the particles number in continuum, and the Coulomb barrier, the exotic structures including the neutron skin and the proton radioactivity are predicted., 45 pages, 17 figures, and 1 table, accepted version for Physical Review C

Collective mass tensors derived in the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (ATDHFB) method are employed in a study of induced fission dynamics. Together with a collective potential determined in deformation-constrained self-consistent mean-field calculations based on nuclear energy density functionals, the mass tensors specify the collective Hamiltonian that governs the time evolution of the nuclear wave function from an initial state at equilibrium deformation, up to scission and the formation of fission fragments. In an illustrative calculation of low-energy induced fission of $^{228}$Th, $^{230}$Th, $^{234}$U, and $^{240}$Pu, we compare the non-perturbative and perturbative cranking ATDHFB mass tensors in the plane of axially-symmetric quadrupole and octupole deformations, as well as the resulting charge yields., Comment: 7 pages, 7 figures. arXiv admin note: text overlap with arXiv:1902.09535

The semi-magic nucleus 219Np was produced in the fusion reaction 187Re(36Ar, 4n)219Np at the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure). A fast electronics system based on waveform digitizers was used in the data acquisition and the sampled pulses were processed by digital algorithms. The reaction products were identified using spatial and time correlations between the implants and subsequent α decays. According to the observed α-decay chain, an energy of E α = 9039 ( 40 ) keV and a half-life of T 1 / 2 = 0.15 − 0.07 + 0.72 ms were determined for 219Np. The deduced proton binding energy of 219Np fits well into the systematics, which gives another evidence of that there is no sub-shell closure at Z = 92 . The influence of the N = 126 shell closure on the stability of Np isotopes is discussed within the framework of α-decay reduced widths.

In recent decades, the study of capture and fusion dynamics in heavy-ion collisions has been a subject of intense experimental and theoretical interests because the heavy-ion capture not only is of central importance for nucleosynthesis but also can reveal rich interplay between nuclear structure and reaction dynamics. Theoretically, the heavy-ion capture and fusion processes at energies near the Coulomb barrier can be treated as a multidimensional barrier penetration problem. The multidimensional barrier penetration process can be described by solving the coupled-channel equations, i.e., the coupled-channel (CC) model. However, for heavy reaction systems, it is necessary to take into account a large number of channels which is not easy to realize in the CC model. Moreover, the structure information of the interacting nuclei are needed as inputs. Therefore, full CC calculations become intractable in many cases including many fusion reactions leading to superheavy nuclei. On the other hand, in the eigenchannel framework, the couplings to other channels split the single potential barrier into a set of discrete barriers. Based on the concept of the barrier distribution, several empirical CC approaches have been developed. Recently, we have developed an empirical coupled-channel (ECC) model and performed a systematic study of capture excitation functions for 220 reaction systems. In this ECC model, an asymmetric Gaussian-form barrier distribution function was used to take effectively into account the effects of inelastic excitation couplings and neutron transfer coupling. Based on the interaction potential between the projectile and the target, empirical formulas were proposed for the parameters of the barrier distribution according to the static and dynamical deformations of the two colliding nuclei. For the vibrational coupling effect and the rotational coupling effect, the parameters of the empirical formulas were given, respectively. For spherical reaction systems (vibrational coupling effect), the width of the barrier distribution increases with the charge product of the reaction system, while for the deformed reaction systems (rotational coupling effect), besides the charge product of the reaction system, the width of the barrier distribution is also related to the static deformation parameters of the projectile and the target. For some reaction systems, the coupling effects of the positive Q -value neutron transfer (PQNT) channels are needed to explain the enhancement of sub-barrier capture cross sections. In this ECC model, the effects of PQNT are simulated by broadening the barrier distribution. Moreover, the positive Q value for one neutron pair transfer is used to broaden the barrier distribution in the present model. Among these 220 reaction systems, there are 89 systems with positive Q value for one neutron pair transfer channel. The calculated capture cross sections of most of these 89 reaction systems are in good agreement with the experimental values, which implies that the Q value for one neutron pair transfer is very important to understanding of the coupling to PQNT channels. Generally speaking, the ECC model together with the empirical formulas for parameters of the barrier distribution works quite well in the description of the capture cross sections at near-barrier energies. This model can provide useful information on capture dynamics and predictions of capture cross sections for the synthesis of superheavy nuclei. In the present paper, we will review this ECC model and its applications.

A new short-lived neutron-deficient isotope Np-220 was synthesized in the fusion-evaporation reaction Re-185(Ar-40, 5n)Np-220 at the gas-filled recoil separator SHANS. Based on the measurement of the correlated alpha-decay chains, the decay properties of Np-220 with E-alpha = 10040(18) keV and T-1/2 = 25(-7)(+14 )mu s were determined, which are in good agreement with theoretical predictions. From the new experimental results coupled with the recently reported alpha-decay data of Np-219,Np-223, the alpha-decay systematics for Np isotopes around N = 126 was established, which allows us for the first time to test the robustness of the N = 126 shell closure in Z = 93 Np isotopes. The results also indicate that, in the region of nuclei with Z >= 83, the proton drip line has been reached for all odd-Z isotopes up to Np.

Low-energy positive and negative parity collective states in the equilibrium minimum, and the dynamics of induced fission of actinide nuclei are investigated in a unified theoretical framework based on the generator coordinate method (GCM) with the Gaussian overlap approximation (GOA). The collective potential and inertia tensor, both at zero and finite temperature, are computed using the self-consistent multidimensionally constrained relativistic mean field (MDC-RMF) model, based on the energy density functional DD-PC1. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. A collective quadrupole-octupole Hamiltonian characterized by zero-temperature axially-symmetric deformation energy surface and perturbative cranking inertia tensor, is used to model the low-lying excitation spectrum. The fission fragment charge distributions are obtained by propagating the initial collective states in time with the time-dependent GCM+GOA that uses the same quadrupole-octupole Hamiltonian, but with the collective potential and inertia tensor computed at finite temperature. The illustrative charge yields of $^{228}$Th, $^{234}$U, $^{240}$Pu, $^{244}$Cm, and $^{250}$Cf are in very good agreement with experiment, and the predicted mass asymmetry is consistent with the result of a recent microscopic study that has attributed the distribution (peak) of the heavier-fragment nuclei to shell-stabilized octupole deformations., Comment: 10 pages, 8 figures. arXiv admin note: text overlap with arXiv:1809.06144

We study the ground state properties, potential energy curves and potential energy surfaces of the superheavy nucleus $^{270}$Hs by using the multidimensionally-constrained relativistic mean-field model with the effective interaction PC-PK1. The binding energy, size and shape as well as single particle shell structure corresponding to the ground state of this nucleus are obtained. $^{270}$Hs is well deformed and exhibits deformed doubly magic feature in the single neutron and proton level schemes. One-dimensional potential energy curves and two-dimensional potential energy surfaces are calculated for $^{270}$Hs with various spatial symmetries imposed. We investigate in detail the effects of the reflection asymmetric and triaxial distortions on the fission barrier and fission path of $^{270}$Hs. When the axial symmetry is imposed, the reflection symmetric and reflection asymmetric fission barriers both show a double-hump structure and the former is higher. However, when triaxial shapes are allowed the reflection symmetric barrier is lowered very much and then the reflection symmetric fission path becomes favorable., Comment: 13 pages, 8 figures

Effective single-particle potentials obtained by self-consistent HFB calculations from the established non-relativistic and relativistic nuclear EDF approaches are incorporated into the microscopic-macroscopic method, a widely and successfully used approach for superheavy nuclei. We determine the Schrodinger-equivalent central and spin-orbit potentials incorporating effective mass effects. The method can be applied to non-relativistic and relativistic mean-fields. A parametrization in terms of the Wood-Saxon form is introduced to derive the proton and neutron potentials, appropriate for the microscopic-macroscopic method. As the first application, the extended microscopic-macroscopic approach is used to calculate the shell corrections in the heaviest nuclei. Constraints on parameters sets for central and spin-orbit potentials are derived for which the shell effects are amplified towards $ Z=120$ .

The α -decay study is an important tool for obtaining information on the nuclear structure of heavy neutron-deficient nuclei. For the N =126 and 124 isotones with even proton number, an intruder state ( π h 9/2 π f 7/2)8+ based on the attractive interaction of f 7/2 protons and f 5/2 neutrons was observed, which increases the binding energy of this configuration with increasing proton number. Additionally, taking into account the octupole correlations, a large-scale shell model calculations predict that the ( π h 9/2 π f 7/2)8+ state lies close or below the ( π h 9 / 2 2 ) 6+ state in the 216Th and 218U. To extend the systematic of the I π =8+ isomeric state in N =124 isotones and search for the most neutron-deficient uranium isotopes, an experiment for the α -decay studies of 215 - 217U was performed at the gas-filled recoil separator SHANS at the Heavy Ion Research Facility in Lanzhou (HIRFL). Heavy ion induced fusion evaporation reactions of the 180W(40Ar, x n)220 - x U ( x =3 - 5) were used to synthesize these neutron-deficient uranium isotopes. The 40Ar beam was delivered by the sector focusing cyclotron of the HIRFL. The evaporation residues recoiled from the thin target were separated in-flight from the primary beam particles by the gas-filled recoil separator SHANS. After passing through two multi-wire proportional counters, the residues were planted into a focal plane detection system. Based on the energy-position-time correlation measurement, the isotopes 215 - 217U were identified. At a beam energy of 187.2 MeV, two α -decaying states were observed in 216U with E α =8.384(30) MeV, T 1/2=

The decay of 218Pa was investigated by means of α and γ spectroscopy. The nucleus was produced in the fusion reaction 40Ar+182W and separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure). The known α decays of 218Pa were measured with improved precision and newly assigned to be originating from the ground state, which clarified the ambiguities in their previous assignments. In addition, a new isomeric state in 218Pa decaying with α-particle energies of 9691(15) keV, 9595(21) keV and a half-life of 135−32+62 μs was identified. The spins and parities of the involved states were tentatively assigned on the basis of the systematic α-decay properties of the odd-proton N=127 isotones and shell model calculations. Keywords: Odd-proton N=127 isotones, Isomeric state, α-particle energy, Half-life, Shell model calculation, Spin and parity

The dynamics of induced fission of $^{226}$Th is investigated in a theoretical framework based on the finite-temperature time-dependent generator coordinate method (TDGCM) in the Gaussian overlap approximation (GOA). The thermodynamical collective potential and inertia tensor at temperatures in the interval $T=0 - 1.25$ MeV are calculated using the self-consistent multidimensionally constrained relativistic mean field (MDC-RMF) model, based on the energy density functional DD-PC1. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Constrained RMF+BCS calculations are carried out in the collective space of axially symmetric quadrupole and octupole deformations for the asymmetric fissioning nucleus $^{226}$Th. The collective Hamiltonian is determined by the temperature-dependent free energy surface and perturbative cranking inertia tensor, and the TDGCM+GOA is used to propagate the initial collective state in time. The resulting charge and mass fragment distributions are analyzed as functions of the internal excitation energy. The model can qualitatively reproduce the empirical triple-humped structure of the fission charge and mass distributions already at $T=0$, but the precise experimental position of the asymmetric peaks and the symmetric-fission yield can only be accurately reproduced when the potential and inertia tensor of the collective Hamiltonian are determined at finite temperature, in this particular case between $T=0.75$ MeV and $T=1$ MeV., 9 pages, 7 figures

The empirical coupled-channel (ECC) model and the universal fusion function (UFF) prescription are used to analyse the data of capture cross sections for reactions ${}^{39}$K$+{}^{181}$Ta and ${}^{46}$K$+{}^{181}$Ta reported recently by A. Wakhle {\it et al.} [Phys. Rev. C 97, 021602(R) (2018)]. The results of the ECC model are in good agreement with the data of ${}^{39}$K$+{}^{181}$Ta while, for ${}^{46}$K$+{}^{181}$Ta, the predictions of the ECC model overestimate the above-barrier capture cross sections. Comparing the reduced data of these two reactions, it is found that the above-barrier cross sections of ${}^{39}$K$+{}^{181}$Ta are consistent with the UFF and are larger than those of ${}^{46}$K$+{}^{181}$Ta. This implies that the capture cross sections of ${}^{46}$K$+{}^{181}$Ta are suppressed at energies above the Coulomb barrier. Furthermore, at sub-barrier energies, the reduced calculated capture cross sections of ${}^{39}$K$+{}^{181}$Ta are a little larger than those of ${}^{46}$K$+{}^{181}$Ta, which is owing to the coupling to the positive $Q$-value two-neutron transfer channel.

In this theoretical study, we establish a correlation between the neutron skin thickness and the nuclear symmetry energy for the even$-$even isotopes of Fe, Ni, Zn, Ge, Se and Kr within the framework of the axially deformed self-consistent relativistic mean field for the non-linear NL3$^*$ and density-dependent DD-ME1 interactions. The coherent density functional method is used to formulate the symmetry energy, the neutron pressure and the curvature of finite nuclei as a function of the nuclear radius. We have performed broad studies for the mass dependence on the symmetry energy in terms of the neutron-proton asymmetry for mass 70 $\leq$ A $\leq$ 96. From this analysis, we found a notable signature of a shell closure at $N$ = 50 in the isotopic chains of Fe, Ni, Zn, Ge, Se and Kr nuclei. The present study reveals an interrelationship between the characteristics of infinite nuclear matter and the neutron skin thickness of finite nuclei, 13 Pages, 07 Figures, and 03 Tables

The study of exotic nuclei---nuclei with the ratio of neutron number $N$ to proton number $Z$ deviating much from that of those found in nature---is at the forefront of nuclear physics research because it can not only reveal novel nuclear properties and thus enrich our knowledge of atomic nuclei, but also help us to understand the origin of chemical elements in the nucleosynthesis. With the development of radioactive ion beam facilities around the world, more and more unstable nuclei become experimentally accessible. Many exotic nuclear phenomena have been observed or predicted in nuclei far from the $\beta$-stability line, such as neutron or proton halos, the shell evolution and changes of nuclear magic numbers, the island of inversion, soft-dipole excitations, clustering effects, new radioactivities, giant neutron halos, the shape decoupling between core and valence nucleons in deformed halo nuclei, etc. In this contribution, I will present a review of theoretical study of exotic nuclear structure. I will first introduce characteristic features and new physics connected with exotic nuclear phenomena: the weakly-bound feature, the large-spatial extension in halo nuclei, deformation effects in halo nuclei, the shell evolution, new radioactivities and clustering effects. Then I will highlight some recent progresses corresponding to these features., Comment: 11 pages, 2 figures; plenary talk given at the 26th International Nuclear Physics Conference (INPC2016), Sep. 11-16, 2016, Adelaide, Australia

The intrinsic level densities of dinuclear systems formed in heavy-ion reactions are calculated using the single-particle spectra obtained with the modified two-center shell model. The role of the mass asymmetry, deformation parameters, and neck size on the level density as well as their quenching with excitation energy are studied. The extracted level density parameter is compared with that obtained in the sudden approximation. The phenomenological parametrization is suggested to estimate the level density parameters for dinuclear systems and strongly deformed nuclear shapes.

We study strange quark matter (SQM) objects ranging from strangelets to strange stars based on our recently proposed unified description. The important interface effects are investigated by adopting a constant surface tension as well as the multiple reflection expansion (MRE) method. It is shown that the properties of SQM objects are strongly affected by the different surface treatments. In the former case, strangelets are more compact, an electric dipole is predicted on the surface of the quark part, and a local minimum of the energy per baryon appears for unusually small values of the surface tension. In the latter case, on the other hand, an electric potential well is formed, and the energy per baryon decreases monotonically with the SQM object's size. It is found that the MRE scenario coincides with the constant-surface-tension one if realistic values are considered. However, the effects of quark depletion on the quark-vacuum interface cannot be solely described by a constant surface tension. Thus we conclude that the MRE scenario is more reasonable.

The dynamic coupling effects on fusion cross sections for reactions $^{32}$S + $^{94,96}$Zr and $^{40}$Ca + $^{94,96}$Zr are studied with the universal fusion function formalism and an empirical coupled channel (ECC) model. An examination of the reduced fusion functions shows that the total effect of couplings to inelastic excitations and neutron transfer channels on fusion in $^{32}$S + $^{94}$Zr ($^{40}$Ca + $^{94}$Zr) is almost the same as that in $^{32}$S + $^{96}$Zr ($^{40}$Ca + $^{96}$Zr). The enhancements of the fusion cross section at sub-barrier energies due to inelastic channel coupling and neutron transfer channel coupling are evaluated separately by using the ECC model. The results show that effect of couplings to inelastic excitations channels in the reactions with $^{94}$Zr as target should be similar as that in the reactions with $^{96}$Zr as target. This implies that the quadrupole deformation parameters $\beta_2$ of $^{94}$Zr and $^{96}$Zr should be similar to each other. However, $\beta_2$'s predicted from the finite-range droplet model, which are used in the ECC model, are quite different. Experiments on $^{48}$Ca + $^{94}$Zr or $^{36}$S + $^{94}$Zr are suggested to solve the puzzling issue concerning $\beta_2$ for $^{94}$Zr., Comment: 8 pages, 5 figures. arXiv admin note: text overlap with arXiv:1504.00756

Complete fusion excitation functions of reactions involving breakup are studied by using the empirical coupled-channel (ECC) model with breakup effects considered. An exponential function with two parameters is adopted to describe the prompt-breakup probability in the ECC model. These two parameters are fixed by fitting the measured prompt-breakup probability or the complete fusion cross sections. The suppression of complete fusion at energies above the Coulomb barrier is studied by comparing the data with the predictions from the ECC model without the breakup channel considered. The results show that the suppression of complete fusion is roughly independent of the target for the reactions involving the same projectile.

© 2016 Owned by the authors, published by EDP Sciences.We developed a cluster model which allows to take into account both shape deformation parameters and cluster degrees of freedom. The model is based on the assumption that the wave function of nucleus can be treated as a superposition of a mononucleus and two-cluster configurations. The model is applied to describe the multiple negative-parity bands in deformed actinides. Special emphasis is made on the investigation of the recently measured positive parity 0+2 rotational band of reflection-asymmetric nature in 240Pu. The results suggest that this band might be understood as the one built on the lowest excited state in mass asymmetry degree of freedom.