Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： We develop the real stabilization method within the framework of the relativistic mean field (RMF) model. With the self-consistent nuclear potentials from the RMF model, the real stabilization method is used to study single-particle resonant states in spherical nuclei. As examples, the energies, widths and wave functions of low-lying neutron resonant states in 120Sn are obtained. These results are compared with those from the scattering phase shift method and the analytic continuation in the coupling constant approach and satisfactory agreements are found.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： Starting from the WKB approximation, a new barrier penetration formula is proposed for poten- tial barriers containing a long-range Coulomb interaction. This formula is especially proper for the barrier penetration with penetration energy much lower than the Coulomb barrier. The penetra- bilities calculated from the new formula agree well with the results from the WKB method. As a first attempt, this new formula is used to evaluate α decay half-lives of atomic nuclei and a good agreement with the experiment is obtained.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： The spherical-box approach is extended to calculate the resonance parameters and the real part of the wave function for single particle resonances in a potential containing the long-range Coulomb interaction. A model potential is taken to demonstrate the ability and accuracy of this approach. The calculated resonance parameters are compared with available results from other methods. It is shown that in the presence of the Coulomb interaction, the spherical-box approach works well for not so broad resonances. In particular, for very narrow resonances, the present method gives resonance parameters in a very high precision.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： The recently observed high-spin rotational bands in odd-A nuclei 247,249Cm and 249Cf [Tandel et al., Phys. Rev. C 82 (2010) 041301R] are investigated by using the cranked shell model (CSM) with the pairing correlations treated by a particle-number conserving (PNC) method in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency ω are reproduced very well by the PNC-CSM calculations. By examining the ω-dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions of valence orbitals to the angular momentum alignment in each major shell, the level crossing and upbending mechanism in each nucleus is understood clearly.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： The shapes of light normal nuclei and Λ hypernuclei are investigated in the (β,γ) deformation plane by using a newly developed constrained relativistic mean field (RMF) model. As examples, the results of some C, Mg, and Si nuclei are presented and discussed in details. We found that for normal nuclei the present RMF calculations and previous Skyrme-Hartree-Fock models predict similar trends of the shape evolution with the neutron number increasing. But some quantitative aspects from these two approaches, such as the depth of the minimum and the softness in the γ direction, differ a lot for several nuclei. For Λ hypernuclei, in most cases, the addition of a Λ hyperon alters slightly the location of the ground state minimum towards the direction of smaller β and softer γ in the potential energy surface E ∼ (β,γ). There are three exceptions, namely, 13C, 23C, and ΛΛ 31Si in which the polarization effect of the additional Λ is so strong that the shapes of these three Λ hypernuclei are drastically different from their corresponding core nuclei.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： For the first time the potential energy surfaces of actinide nuclei in the (β20, β22, β30) deformation space are obtained from a multi-dimensional constrained covariant density functional theory. With this newly developed theory we are able to explore the importance of the triaxial and octupole shapes simultaneously along the whole fission path. It is found that besides the octupole deformation, the triaxiality also plays an important role upon the second fission barriers. The outer barrier as well as the inner barrier are lowered by the triaxial deformation compared with axially symmetric results. This lowering effect for the reflection asymmetric outer barrier is 0.5 ∼ 1 MeV, accounting for 10 ∼ 20% of the barrier height. With the inclusion of the triaxial deformation, a good agreement with the data for the outer barriers of actinide nuclei is achieved.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： The rotational bands in nuclei with Z ≈ 100 are investigated systematically by using a cranked shell model (CSM) with the pairing correlations treated by a particle-number conserving (PNC) method, in which the blocking effects are taken into account exactly. By fitting the experimental single-particle spectra in these nuclei, a new set of Nilsson parameters (κ and μ) and deformation parameters (ε2 and ε4) are proposed. The experimental kinematic moments of inertia for the rotational bands in even-even, odd-A and odd-odd nuclei, and the bandhead energies of the 1- quasiparticle bands in odd-A nuclei, are reproduced quite well by the PNC-CSM calculations. By analyzing the ω-dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions of valence orbitals in each major shell to the angular momentum alignment, the upbending mechanism in this region is understood clearly.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： By using a newly developed di-nuclear system model with a dynamical potential energy surface— the DNS-DyPES model, hot fusion reactions for synthesizing superheavy nuclei (SHN) with the charge number Z = 112–120 are studied. The calculated evaporation residue cross sections are in good agreement with available data. In the reaction 50Ti+249Bk → 299−x119 + xn, the maximal evaporation residue (ER) cross section is found to be about 0.11 pb for the 4n-emission channel. For projectile-target combinations producing SHN with Z = 120, the ER cross section increases with the mass asymmetry in the incident channel increasing. The maximal ER cross sections for 58Fe+244Pu and 54Cr+248Cm are relatively small (less than 0.01 pb) and those for 50Ti+249Cf and 50Ti+251Cf are about 0.05 and 0.25 pb, respectively.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： The pseudospin symmetry is a relativistic dynamical symmetry connected with the small com- ponent of the Dirac spinor. The origin of pseudospin symmetry in single particle bound states in atomic nuclei has been revealed and studied extensively. By examining the zeros of Jost functions corresponding to the small components of Dirac wave functions and phase shifts of continuum states, we show that the pseudospin symmetry in single particle resonant states in nuclei is conserved when the attractive scalar and repulsive vector potentials have the same magnitude but opposite sign. The exact conservation and the breaking of pseudospin symmetry are illustrated for single particle resonances in spherical square-well and Woods-Saxon potentials.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-08-22
Abstract： The non-axial reflection-asymmetric β32 shape in some transfermium nuclei with N = 150, namely 246Cm, 248Cf, 250Fm, and 252No are investigated with multidimensional constrained covariant den- sity functional theories. By using the density-dependent point coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of 248Cf and 250Fm, the non-axial octupole deformation parameter β32 > 0.03 and the energy gain due to the β32 distortion is larger than 300 keV. In 246Cm and 252No, shallow β32 minima are found. The occurrence of the non-axial octupole β32 correlations is mainly from a pair of neutron orbitals [734]9/2 (νj15/2) and [622]5/2 (νg9/2) which are close to the neutron Fermi surface and a pair of proton orbitals [521]3/2 (πf7/2) and [633]7/2 (πi13/2) which are close to the proton Fermi surface. The dependence of the non-axial octupole effects on the form of energy density functional and on the parameter set is also studied.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： Multi-dimensional constrained covariant density functional theories were developed recently. In these theories, all shape degrees of freedom βλμ deformations with even μ are allowed, e.g., β20, β22, β30, β32, β40, β42, β44, and so on and the CDFT functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. In this contri- bution, some applications of these theories are presented. The potential energy surfaces of actinide nuclei in the (β20 , β22 , β30 ) deformation space are investigated. It is found that besides the octupole deformation, the triaxiality also plays an important role upon the second fission barriers. The non-axial reflection-asymmetric β32 shape in some transfermium nuclei with N = 150, namely 246Cm, 248Cf, 250Fm, and 252No are studied.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： In this contribution we present some results on the study of pseudospin symmetry (PSS) in single particle resonant states. The PSS is a relativistic dynamical symmetry connected with the small component of the nucleon Dirac wave function. Many efforts have been made to study this symmetry in bound states. We recently gave a rigorous justification of the PSS in single particle resonant states by examining the zeros of Jost functions corresponding to the small components of the radial Dirac wave functions and phase shifts of continuum states [1]. We have shown that the PSS in single particle resonant states in nuclei is conserved when the attractive scalar and repulsive vector potentials have the same magnitude but opposite sign. Examples of exact conservation and breaking of this symmetry in single particle resonances are given for spherical square-well and Woods-Saxon potentials.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： We have developed multi-dimensional constrained covariant density functional theories (MDC-CDFT) for finite nuclei in which the shape degrees of freedom βλμ with even μ, e.g., β20, β22, β30, β32, β40, etc., can be described simultaneously. The functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. For the pp channel, either the BCS approach or the Bogoliubov transformation is implemented. The MDC-CDFTs with the BCS approach for the pairing (in the following labelled as MDC-RMF models with RMF standing for “relativistic mean field”) have been applied to investigate multi-dimensional potential energy surfaces and the non-axial octupole Y32-correlations in N = 150 isotones. In this contribution we present briefly the formalism of MDC-RMF models and some results from these models. The potential energy surfaces with and without triaxial deformations are compared and it is found that the triaxiality plays an important role upon the second fission barriers of actinide nuclei. In the study of Y32-correlations in N = 150 isotones, it is found that, for 248Cf and 250Fm, β32 > 0.03 and the energy is lowered by the β32 distortion by more than 300 keV; while for 246Cm and 252No, the pocket with respect to β32 is quite shallow.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： AdeformedrelativisticHartree-Bogoliubovtheoryincontinuumhasbeendevelopedfor the study of neutron halos in deformed nuclei and the halo phenomenon in deformed weakly bound nuclei is investigated. Magnesium and neon isotopes are studied and some results are presented for the deformed neutron-rich and weakly bound nuclei 44Mg and 36Ne. The core of the former nucleus is prolate, but the halo has a slightly oblate shape. This indicates a decoupling of the halo orbitals from the deformation of the core. The generic conditions for the existence of halos in deformed nuclei and for the occurrence of this decoupling effect are discussed.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： The effects of nuclear superfluidity on antimagnetic rotation bands in 105Cd and 106Cd are in- vestigated by the cranked shell model with the pairing correlations and the blocking effects treated by a particle-number conserving method. The experimental moments of inertia and the reduced B(E2) transition values are excellently reproduced. The nuclear superfluidity is essential to repro- duce the experimental moments of inertia. The two-shears-like mechanism for the antimagnetic rotation is investigated by examining the shears angle, i.e., the closing of the two proton hole angular momenta, and its sensitive dependence on the nuclear superfluidity is revealed.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： Background: The pseudospin symmetry (PSS) has been studied extensively for bound states. Recently we justified rigorously that the PSS in single particle resonant states is exactly conserved when the attractive scalar and repulsive vector potentials of the Dirac Hamiltonian have the same magnitude but opposite sign [Phys. Rev. Lett. 109, 072501 (2012)]. Purpose: To understand more deeply the PSS in single particle resonant states, we focus on several issues related to the exact conservation and breaking mechanism of the PSS in single particle resonances. In particular, we are interested in how the energy and width splittings of PS partners depend on the depth of the scalar and vector potentials. Methods: We investigate the asymptotic behaviors of radial Dirac wave functions. Spherical square well poten- tials are employed in which the PSS breaking part in the Jost function can be well isolated. By examining the zeros of Jost functions corresponding to small components of the radial Dirac wave functions, general properties of the PSS are analyzed. Results: By examining the Jost function, the occurrence of intruder orbitals is explained and it is possible to trace continuously the PSS partners from the PSS limit to the case with a finite potential depth. The dependence of the PSS in resonances as well as in bound states on the potential depth is investigated systematically. We find a threshold effect in the energy splitting and an anomaly in the width splitting of pseudospin partners when the depth of the single particle potential varies from zero to a finite value. Conclusions: The conservation and the breaking of the PSS in resonant states and bound states share some similar properties. The appearance of intruder states can be explained by examining the zeros of Jost functions. Origins of the threshold effect in the energy splitting and the anomaly in the width splitting of PS partners, together with many other problems, are still open and should be further investigated.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： The pseudospin symmetry (PSS) is a relativistic dynamical symmetry directly connected with the small component of the nucleon Dirac wave function. Much effort has been made to study this symmetry in bound states. Recently, a rigorous justification of the PSS in single particle resonant states was achieved by examining the asymptotic behaviors of the radial Dirac wave functions: The PSS in single particle resonant states in nuclei is conserved exactly when the attractive scalar and repulsive vector potentials have the same magnitude but opposite sign. Several issues related to the exact conservation and breaking mechanism of the PSS in single particle resonances were investigated by employing spherical square well potentials in which the PSS breaking part can be well isolated in the Jost function. A threshold effect in the energy splitting and an anomaly in the width splitting of pseudospin partners were found when the depth of the square well potential varies from zero to a finite value.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： In this contribution we present some results of potential energy sur- faces of actinide and transfermium nuclei from multi-dimensional constrained relativistic mean field (MDC-RMF) models. Recently we developed multi-dimensional constrained covariant density func- tional theories (MDC-CDFT) in which all shape degrees of freedom βλμ with even μ are allowed and the functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent cou- plings. In MDC-RMF models, the pairing correlations are treated with the BCS method. With MDC-RMF models, the potential energy surfaces of even-even actinide nuclei were investigated and the effect of triaxiality on the fission barriers in these nuclei was discussed. The non-axial reflection-asymmetric β32 shape in some βλμ =0 β22 ̸=0 β20 >0 β30 ̸=0 β20 <0 β32 ̸=0 β40 >0 β20 ≫0 transfermium nuclei with N = 150, namely and 252No were also studied.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： Background: Many different shape degrees of freedom play crucial roles in determining the nuclear ground state and saddle point properties and the fission path. For the study of nuclear potential energy surfaces, it is desirable to have microscopic and self-consistent models in which all known important shape degrees of freedom are included. Purpose: By breaking both the axial and the spatial reflection symmetries simultaneously, we develop multidimensionally-constrained relativistic mean field (MDC-RMF) models. Methods: The nuclear shape is assumed to be invariant under the reversion of x and y axes, i.e., the intrinsic symmetry group is V4 and all shape degrees of freedom βλμ with even μ, such as β20, β22, β30, β32, β40, ..., are included self-consistently. The single-particle wave functions are expanded in an axially deformed harmonic oscillator (ADHO) basis. The RMF functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the nonlinear or density-dependent couplings. The pairing effects are taken into account with the BCS approach. Results: The one-, two, and three-dimensional potential energy surfaces of 240Pu are illustrated for numerical checks and for the study of the effect of the triaxiality on the fission barriers. Potential energy curves of even-even actinide nuclei around the first and second fission barriers are studied systematically. Besides the first ones, the second fission barriers in these nuclei are also lowered considerably by the triaxial deformation. This lowering effect is independent of the effective interactions used in the RMF functionals. Further discussions are made about different predictions on the effect of the triaxiality between the macroscopic-microscopic and MDC-RMF models, possible discontinuities on PES’s from self-consistent approaches, and the restoration of broken symmetries. Conclusions: MDC-RMF models give a reasonably good description of fission barriers of even-even actinide nuclei. It is important to include both the nonaxial and the reflection asymmetric shapes simultaneously for the study of potential energy surfaces and fission barriers of actinide nuclei and of those in unknown mass regions such as, e.g., superheavy nuclei.
Peer Review Status:Awaiting Review
Subjects: Physics >> Nuclear Physics submitted time 2017-07-30
Abstract： A large number of complete fusion excitation functions of reactions including the breakup channel were measured in recent decades, especially in the last few years. It allows us to investigate the systematic behavior of the breakup effects on the complete fusion cross sections. To this end, we perform a systematic study of the breakup effects on the complete fusion cross sections at energies above the Coulomb barrier. The reduced fusion functions F(x) are compared with the universal fusion functions which are used as a uniform standard reference. The complete fusion cross sections at energies above the Coulomb barrier are suppressed by the breakup of projectiles. This suppression effect for reactions induced by the same projectile is independent of the target and mainly determined by the lowest energy breakup channel of the projectile. There holds a good exponential relation between the suppression factor and the energy corresponding to the lowest breakup threshold.
Peer Review Status:Awaiting Review
Hits
Hits
Downloads
Comment