本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位...本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位旋标量对力对于恢复SU(4)对称性从而重现实验上42Ca的低能量超级GT态至关重要。同位旋标量对力会使自旋反转的跃迁组分混合进入低能量GT态,从而增强低能量GT态的集体性,极大地增加其跃迁强度。同时,由于同位旋标量对力具有吸引性质,会减小低能量GT态的激发能。对于SD跃迁,同位旋标量对力对其激发能和跃迁强度的影响均不明显。展开更多
Using the axially deformed relativistic Hartree-Fock-Bogoliubov(D-RHFB)model,we explore the mechanism behind the parity inversion and halo occurrence in^(11)Be,which are well reproduced by the RHF Lagrangian PKA1.It i...Using the axially deformed relativistic Hartree-Fock-Bogoliubov(D-RHFB)model,we explore the mechanism behind the parity inversion and halo occurrence in^(11)Be,which are well reproduced by the RHF Lagrangian PKA1.It is illustrated that evidently enhanced deformation effects by theπ-pseudo-vector andρ-tensor couplings in PKA1 are crucial for correctly describing both the even-parity ground state(GS)and the neutron halo of^(11)Be.Coupling with the deformation,the intrude 1d_(5/2)component largely enhances the couplings between the evenparity orbit 1/2_(2)^(+)and the nuclear core to ensure an even-parity GS,whereas the 2s_(1/2)component therein dominates the halo formation in^(11)Be.Moreover,the deformed halo in^(11)Be is found to be stabilized by the attractive inherent correlations between the 1d_(5/2)and 2s_(1/2)components of the halo orbit 1/2_(2)^(+),instead of pairing correlations,which paves a new way for understanding the halo pictures in deformed unstable nuclei.展开更多
The restoration of pseudo-spin symmetry(PSS) along the N = 32 and N = 34 isotonic chains and the physics behind are studied by applying the relativistic Hartree-Fock theory with the effective Lagrangian PKA1. Taking t...The restoration of pseudo-spin symmetry(PSS) along the N = 32 and N = 34 isotonic chains and the physics behind are studied by applying the relativistic Hartree-Fock theory with the effective Lagrangian PKA1. Taking the proton pseudo-spin partners(π2s1/2,π1d3/2) as candidates, the systematic restoration of PSS along both isotonic chains is found from sulphur(S) to nickel(Ni), while an obvious PSS violation from silicon(Si) to sulphur is discovered near the drip lines. The effects of the tensor force components are investigated, introduced naturally by the Fock terms, which can only partially interpret the systematics from calcium to nickel, whereas they fail for the overall trends. Further analysis following the Schrodinger-like equation of the lower component of Dirac spinor shows that contributions from the Hartree terms dominate the overall systematics of the PSS restoration. Such effects can be self-consistently interpreted by the evolution of the proton central density profiles along both isotonic chains. In particular, the PSS violation is found to tightly relate to the dramatic changes from the bubble-like density profiles in silicon to the central-bumped ones in sulphur.展开更多
The rich phenomena of deformations in neutron-deficient krypton isotopes,such as shape evolution with neutron number and shape coexistence,have attracted the interest of nuclear physicists for decades.It is interestin...The rich phenomena of deformations in neutron-deficient krypton isotopes,such as shape evolution with neutron number and shape coexistence,have attracted the interest of nuclear physicists for decades.It is interesting to study such shape phenomena using a novel way,e.g.by thermally exciting the nucleus.In this work,we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach,and apply this approach for the study of shape evolution in ^(72,74)Kr with increasing temperature.For ^(72)Kr,with temperature increasing,the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T^0.9 Me V,and then changes from oblate to spherical at T^2.1 Me V.For ^(74)Kr,its global minimum is at quadrupole deformation β_2^-0.14 and abruptly changes to spherical at T^1.7 MeV.The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc =0.6?p(0),where ?p(0) is the proton pairing gap at zero temperature.The signatures of the above pairing transition and shape changes can be found in the specific heat curve.The single-particle level evolutions with temperature are presented.展开更多
An isoratio method, i.e., the isotopic(isotonic) ratio among three isotopes(isotones), is proposed to study the free energy and temperature effects in the intermediate mass fragments produced in heavy-ion collisions. ...An isoratio method, i.e., the isotopic(isotonic) ratio among three isotopes(isotones), is proposed to study the free energy and temperature effects in the intermediate mass fragments produced in heavy-ion collisions. The parameterizations for the free energy of nucleus at low temperature, which have been proposed in the framework of the density functional theory using the SKM skymre interaction, are adopted to calculate the temperature-dependent free energy of fragment. By analyzing the measured yields of fragments in the 140 A MeV ^(58),^(64) Ni +~9Be reactions,it is verified that the free energy in the isoratio is almost the same for different reactions. A temperature-dependent pairing-energy is introduced into the parameterizations for free energy, which reveals that the weakened pairing energy at the low temperature accounts for the weakened or disappearing odd-even staggering in isoratio.展开更多
The relativistic mean field(RMF)model has achieved great success in describing various nuclear phenomena.However,several serious defects are common.For instance,the pseudo-spin symmetry of high-l orbits is distinctly ...The relativistic mean field(RMF)model has achieved great success in describing various nuclear phenomena.However,several serious defects are common.For instance,the pseudo-spin symmetry of high-l orbits is distinctly violated in general,leading to spurious shell closures N Z 58 and 92.This leads to problems in describing structure properties,including shell structures,nuclear masses,etc.Guided by the pseudo-spin symmetry restoration[Geng et al.,Phys.Rev.C,100:051301(2019)],a new RMF Lagrangian DD-LZ1 is developed by considering the density-dependent meson-nucleon coupling strengths.With the newly obtained RMF Lagrangian DD-LZ1,satisfactory descriptions can be obtained for the bulk properties of nuclear matter and finite nuclei.In particular,significant improvements on describing the single-particle spectra are achieved by DD-LZ1.In particular,the spurious shell closures Z 58 and 92,commonly found in previous RMF calculations,are eliminated by the new effective interaction DD-LZ1,and consistently the pseudo-spin symmetry(PSS)around the Fermi levels is reasonably restored for both low-l and high-l orbits.Moreover,the description of nuclear masses is also notably improved by DD-LZ1,as compared to the other RMF Lagrangians.展开更多
基金Supported by the National Key Basic Research Programme of China under Grant No 2007CB815000, the National Natural Science Foundation of China under Grant Nos 10435010, 10775004 and 10221003.
文摘本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位旋标量对力对于恢复SU(4)对称性从而重现实验上42Ca的低能量超级GT态至关重要。同位旋标量对力会使自旋反转的跃迁组分混合进入低能量GT态,从而增强低能量GT态的集体性,极大地增加其跃迁强度。同时,由于同位旋标量对力具有吸引性质,会减小低能量GT态的激发能。对于SD跃迁,同位旋标量对力对其激发能和跃迁强度的影响均不明显。
基金partly supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB34000000)the National Natural Science Foundation of China(12275111)the Fundamental Research Funds for the Central Universities(lzujbky-2021–sp41,lzujbky-2021–sp36)。
文摘Using the axially deformed relativistic Hartree-Fock-Bogoliubov(D-RHFB)model,we explore the mechanism behind the parity inversion and halo occurrence in^(11)Be,which are well reproduced by the RHF Lagrangian PKA1.It is illustrated that evidently enhanced deformation effects by theπ-pseudo-vector andρ-tensor couplings in PKA1 are crucial for correctly describing both the even-parity ground state(GS)and the neutron halo of^(11)Be.Coupling with the deformation,the intrude 1d_(5/2)component largely enhances the couplings between the evenparity orbit 1/2_(2)^(+)and the nuclear core to ensure an even-parity GS,whereas the 2s_(1/2)component therein dominates the halo formation in^(11)Be.Moreover,the deformed halo in^(11)Be is found to be stabilized by the attractive inherent correlations between the 1d_(5/2)and 2s_(1/2)components of the halo orbit 1/2_(2)^(+),instead of pairing correlations,which paves a new way for understanding the halo pictures in deformed unstable nuclei.
基金Supported by National Natural Science Foundation of China(11675065,11711540016)
文摘The restoration of pseudo-spin symmetry(PSS) along the N = 32 and N = 34 isotonic chains and the physics behind are studied by applying the relativistic Hartree-Fock theory with the effective Lagrangian PKA1. Taking the proton pseudo-spin partners(π2s1/2,π1d3/2) as candidates, the systematic restoration of PSS along both isotonic chains is found from sulphur(S) to nickel(Ni), while an obvious PSS violation from silicon(Si) to sulphur is discovered near the drip lines. The effects of the tensor force components are investigated, introduced naturally by the Fock terms, which can only partially interpret the systematics from calcium to nickel, whereas they fail for the overall trends. Further analysis following the Schrodinger-like equation of the lower component of Dirac spinor shows that contributions from the Hartree terms dominate the overall systematics of the PSS restoration. Such effects can be self-consistently interpreted by the evolution of the proton central density profiles along both isotonic chains. In particular, the PSS violation is found to tightly relate to the dramatic changes from the bubble-like density profiles in silicon to the central-bumped ones in sulphur.
基金Supported by National Natural Science Foundation of China(11105042,11305161,11505157)Open Fund of Key Laboratory of Time and Frequency Primary Standards,CASSupport from Henan Administration of Foreign Experts Affairs
文摘The rich phenomena of deformations in neutron-deficient krypton isotopes,such as shape evolution with neutron number and shape coexistence,have attracted the interest of nuclear physicists for decades.It is interesting to study such shape phenomena using a novel way,e.g.by thermally exciting the nucleus.In this work,we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach,and apply this approach for the study of shape evolution in ^(72,74)Kr with increasing temperature.For ^(72)Kr,with temperature increasing,the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T^0.9 Me V,and then changes from oblate to spherical at T^2.1 Me V.For ^(74)Kr,its global minimum is at quadrupole deformation β_2^-0.14 and abruptly changes to spherical at T^1.7 MeV.The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc =0.6?p(0),where ?p(0) is the proton pairing gap at zero temperature.The signatures of the above pairing transition and shape changes can be found in the specific heat curve.The single-particle level evolutions with temperature are presented.
基金Supported by the Program for Science and Technology Innovation Talents in Universities of Henan Province under Grant No.13HASTIT046the Creative Experimental Project of National Undergraduate Students(CEPNU201510476017)
文摘An isoratio method, i.e., the isotopic(isotonic) ratio among three isotopes(isotones), is proposed to study the free energy and temperature effects in the intermediate mass fragments produced in heavy-ion collisions. The parameterizations for the free energy of nucleus at low temperature, which have been proposed in the framework of the density functional theory using the SKM skymre interaction, are adopted to calculate the temperature-dependent free energy of fragment. By analyzing the measured yields of fragments in the 140 A MeV ^(58),^(64) Ni +~9Be reactions,it is verified that the free energy in the isoratio is almost the same for different reactions. A temperature-dependent pairing-energy is introduced into the parameterizations for free energy, which reveals that the weakened pairing energy at the low temperature accounts for the weakened or disappearing odd-even staggering in isoratio.
基金Supported by National Natural Science Foundation of China(11675065,11875152,11905088)Fundamental Research Funds for the central universities(lzujbky-2019-11)the Supercompuer Center of HIRFL。
文摘The relativistic mean field(RMF)model has achieved great success in describing various nuclear phenomena.However,several serious defects are common.For instance,the pseudo-spin symmetry of high-l orbits is distinctly violated in general,leading to spurious shell closures N Z 58 and 92.This leads to problems in describing structure properties,including shell structures,nuclear masses,etc.Guided by the pseudo-spin symmetry restoration[Geng et al.,Phys.Rev.C,100:051301(2019)],a new RMF Lagrangian DD-LZ1 is developed by considering the density-dependent meson-nucleon coupling strengths.With the newly obtained RMF Lagrangian DD-LZ1,satisfactory descriptions can be obtained for the bulk properties of nuclear matter and finite nuclei.In particular,significant improvements on describing the single-particle spectra are achieved by DD-LZ1.In particular,the spurious shell closures Z 58 and 92,commonly found in previous RMF calculations,are eliminated by the new effective interaction DD-LZ1,and consistently the pseudo-spin symmetry(PSS)around the Fermi levels is reasonably restored for both low-l and high-l orbits.Moreover,the description of nuclear masses is also notably improved by DD-LZ1,as compared to the other RMF Lagrangians.
