We systematically studied the evaporation residue cross sections of ^(48)Ca-induced reactions on lanthanide and actinide target nuclei under the Dinuclear System(DNS)model framework to check the reliability and applic...We systematically studied the evaporation residue cross sections of ^(48)Ca-induced reactions on lanthanide and actinide target nuclei under the Dinuclear System(DNS)model framework to check the reliability and applicability of the model.To produce new proton-rich Fl and Lv isotopes through hot fusion reactions in the superheavy element region with Z≥104,we utilized the reactions ^(48)Ca+^(236,238,239) Pu and ^(48)Ca+^(242,243,244,250) Cm.However,owing to the detection limit of available equipment(0.1 pb),only 283Fl and 287−289Lv,which have the maximum evaporation residue cross section values of 0.149,0.130,9.522,and 0.309 pb,respectively,can be produced.Furthermore,to produce neutron-deficient isotopes of actinides near the proton drip line with Z=93−100,we attempted to generate the new isotopes(224−227Pu,228−232,237Cm)using the reactions ^(48)Ca+180,182,183 W and ^(48)Ca+^(184,186,187,192) Os.The maximum evaporation residue cross section values are 0.07,0.06,0.26,and 0.30 nb for the former set of reactions,and 1.96 pb,5.73 pb,12.16 pb,19.39 pb,54.79 pb,and 6.45 nb for the latter,respectively.These results are expected to provide new information for the future synthesis of unknown neutron-deficient isotopes.展开更多
The multinucleon transfer reaction in the collisions of 40 Ca+^124 Sn at Ec.m.= 128.5 MeV is investigated using the improved quantum molecular dynamics model. The measured angular distributions and isotopic distributi...The multinucleon transfer reaction in the collisions of 40 Ca+^124 Sn at Ec.m.= 128.5 MeV is investigated using the improved quantum molecular dynamics model. The measured angular distributions and isotopic distributions of the products are reproduced reasonably well by the calculations. The multinucleon transfer reactions of 40 Ca+^112 Sn, 58 Ni+^112 Sn, 106 Cd+^112 Sn, and 48 Ca+^112 Sn are also studied. This demonstrates that the combinations of neutron-deficient projectile and target are advantageous for the production of exotic neutron-deficient nuclei near N,Z =50. The charged particles’ emission plays an important role at small impact parameters in the de-excitation processes of the system. The production cross sections of the exotic neutron-deficient nuclei in multinucleon transfer reactions are much larger than those measured in the fragmentation and fusion-evaporation reactions. Several new neutron-deficient nuclei can be produced in the 106 Cd+^112 Sn reaction. The corresponding production cross sections for the new neutron-deficient nuclei,101,112 Sb,103 Te,and 106,107) I,are 2.0 nb,4.1 nb,6.5 nb,0.4 μb and 1.0 μb,respectively.展开更多
The future experimental campaign with the SAMURAI setup at RIKEN will explore a wide range of neutron-deficient nuclei with a particular focus on the most critical(p, γ) reaction rates relevant to the astrophysical r...The future experimental campaign with the SAMURAI setup at RIKEN will explore a wide range of neutron-deficient nuclei with a particular focus on the most critical(p, γ) reaction rates relevant to the astrophysical rp-process in type-I X-ray bursts(XRB). Intense radioactive-ion(RI) beams at an energy of a few hundred Me V/nucleon will be deployed to populate proton-unbound states in the nuclei of interest through the Coulomb excitation or nucleon-removal processes. The decay of these states into a proton and a heavy residue will be measured using complete kinematics and the information about time reversal proton-capture process will be obtained. This method will provide the vital experimental data on the resonances, which dominate the stellar(p, γ) reaction rates, as well as on the direct proton-capture process for some other cases. The experimental setup will utilize for the first time the High-Resolution90?-mode of the SAMURAI spectrometer in combination with the existing detection systems, including custom-designed Si-strip detectors for simultaneous detection and tracking of heavy ions and protons emitted from the target. The details of the experimental method and the utilized apparatus are discussed in this paper.展开更多
In this contribution I would like to review briefly our recent studies on nuclear α formation probabilities in heavy nuclei and their indication on the underlying structure of the nuclei involved.In particular, I wil...In this contribution I would like to review briefly our recent studies on nuclear α formation probabilities in heavy nuclei and their indication on the underlying structure of the nuclei involved.In particular, I will show that the empirical α-formation probabilities, which can be extracted from experimental half-lives, exhibit a rather smooth function with changing proton or neutron numbers. This allows us to distinguish the role played by pairing collectivity in the clustering process. The sudden hindrance of the clustering of the nucleons around the N = 126 shell closure is due to the fact that the configuration space does not allow a proper manifestation of the pairing collectivity. The influence of the Z = 82 shell closure on the α formation properties will also be discussed. Moreover, we have evaluated the α-decay fine structure to excited 0+states in Hg and Rn isotopes as well as the α-decay from the excited 0+states in the mother nucleus. It is thus found that the α decay is sensitive to the mixture of configurations corresponding to different nuclear shapes.展开更多
Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in...Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0＋ states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes （except the ground state of 72Kr）, the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.展开更多
Many isotopes of Np,Pu,Am,and Cm around the N=126 shell still have not been produced in the laboratory.This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np,Pu,Am,and Cm pr...Many isotopes of Np,Pu,Am,and Cm around the N=126 shell still have not been produced in the laboratory.This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np,Pu,Am,and Cm produced in the proton-induced spallations of transuranium elements.The isospin-dependent quantum molecular dynamics(IQMD)model is applied to study the dynamical process of reaction,and the subsequent decay process is simulated by the GEMINI++model.The IQMD-GEMINI++model is applied to calculate the cross section,kinetic energy,and angular distribution of the isotopic productions around N=126.The Lindhand,Scharff,and Schiott theory is applied to calculate the energy loss of different heavy nuclei in the target material.A comparison between the data and the calculations shows that the IQMD-GEMINI++model can reproduce the production cross sections of the neutron-deficient nuclei in spallation within approximately 1.5 orders of magnitude.The maximum cross section of the undiscovered isotopes of Np,Pu,Am,and Cm is about 10-5 mb,while the kinetic energies of the productions are all less than 16 MeV.The angular distribution shows that the emission direction of production is mostly at a backward angle.The range of production in the target is within the range of 10-7to 10-5cm.This range is the effective target thickness for the online identification of undiscovered isotopes.Based on the effective thickness of the target and assuming an intensity of 120μA for the proton beam,the yields of the undiscovered neutron-deficient nuclei are calculated.Productions of the undiscovered isotopes of Np,Pu,Am,and Cm by the proton-induced spallations of transuranium elements are feasible.However,experimental techniques for online identification of neutron-deficient nuclei produced in proton-induced spallation should be developed.展开更多
Nuclei in the light actinide region with Z 92，N 134 are predicted to be candidates for shape coexistence[1],some nuclei in this region are also predicted to have stable octupole deformation[2]. Actinide nuclei with...Nuclei in the light actinide region with Z 92，N 134 are predicted to be candidates for shape coexistence[1],some nuclei in this region are also predicted to have stable octupole deformation[2]. Actinide nuclei with N=134have been produced up to plutonium (228Pu), and the lightest plutonium isotope and neptunium isotope discoveredso far are 228Pu and 225Np respectively. A campaign has been started to investigate the nuclei in this region. Thereaction 20Ne + 209Bi was used to produce 224Np (N=131) in fusion-evaporation reaction as the first step.展开更多
This study investigates the optimal projectile/target combination for the production of new neutron-deficient isotopes of superheavy nuclei(SHN). To this end, the dependence of the evaporation residue cross-section(ER...This study investigates the optimal projectile/target combination for the production of new neutron-deficient isotopes of superheavy nuclei(SHN). To this end, the dependence of the evaporation residue cross-section(ERCS) used to synthesize SHN on the mass asymmetry and the isospin of colliding nuclei are analyzed within the dinuclear system(DNS) concept. The predicted ERCSs for the production of new neutron-deficient isotopes of SHN were found to be quite large with the ^(36) S projectile, and the cross-section of SHN decreases slowly with the charge of compound nuclei owing to the increase in their survival probability,. Wsur is not canceled by the decreasing probability, PCN, that the system will evolve from a touching configuration to the compound nucleus in competition with the quasifission process.展开更多
The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected...The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected by the DIAMANT CsI ball,Neutron Wall,and the EXOGAM Ge clover array,respectively.In addition to the previously reported levels in 91Ru,new low-to-medium spin states were observed.Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91 Ru.The low-spin states of 91 Ru exhibit a scheme of multi-quasiparticle excitations,which is very similar to that of the neighboring N=47 isotone.These excitations have been interpreted in terms of the shell model.The calculations performed in the configuration space(p3/2,f5/2,p1/2,g9/2)reproduce the experimental excitation energies reasonably well,supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurationsπ(g9/2)^-2v(g9/2^-1 and v(g9/2)^-3.展开更多
The structures of the neutron deficient Nd isotopes of A=128～140 are studied in a schematic hamiltonian in the interacting boson model. The level structure and E2 transitions can be well described in the sch...The structures of the neutron deficient Nd isotopes of A=128～140 are studied in a schematic hamiltonian in the interacting boson model. The level structure and E2 transitions can be well described in the scheme. In particular, the backbending in the ground state band is well reproduced.展开更多
基金National Natural Science Foundation of China(Nos.12175064 and U2167203)Hunan Outstanding Youth Science Foundation(No.2022JJ10031).
文摘We systematically studied the evaporation residue cross sections of ^(48)Ca-induced reactions on lanthanide and actinide target nuclei under the Dinuclear System(DNS)model framework to check the reliability and applicability of the model.To produce new proton-rich Fl and Lv isotopes through hot fusion reactions in the superheavy element region with Z≥104,we utilized the reactions ^(48)Ca+^(236,238,239) Pu and ^(48)Ca+^(242,243,244,250) Cm.However,owing to the detection limit of available equipment(0.1 pb),only 283Fl and 287−289Lv,which have the maximum evaporation residue cross section values of 0.149,0.130,9.522,and 0.309 pb,respectively,can be produced.Furthermore,to produce neutron-deficient isotopes of actinides near the proton drip line with Z=93−100,we attempted to generate the new isotopes(224−227Pu,228−232,237Cm)using the reactions ^(48)Ca+180,182,183 W and ^(48)Ca+^(184,186,187,192) Os.The maximum evaporation residue cross section values are 0.07,0.06,0.26,and 0.30 nb for the former set of reactions,and 1.96 pb,5.73 pb,12.16 pb,19.39 pb,54.79 pb,and 6.45 nb for the latter,respectively.These results are expected to provide new information for the future synthesis of unknown neutron-deficient isotopes.
基金Supported by National Natural Science Foundation of China(11635003,11025524,11161130520)the National Basic Research Program of China(2010CB832903)the European Commissions 7th Framework Programme(FP7-PEOPLE-2010-IRSES)(269131)
文摘The multinucleon transfer reaction in the collisions of 40 Ca+^124 Sn at Ec.m.= 128.5 MeV is investigated using the improved quantum molecular dynamics model. The measured angular distributions and isotopic distributions of the products are reproduced reasonably well by the calculations. The multinucleon transfer reactions of 40 Ca+^112 Sn, 58 Ni+^112 Sn, 106 Cd+^112 Sn, and 48 Ca+^112 Sn are also studied. This demonstrates that the combinations of neutron-deficient projectile and target are advantageous for the production of exotic neutron-deficient nuclei near N,Z =50. The charged particles’ emission plays an important role at small impact parameters in the de-excitation processes of the system. The production cross sections of the exotic neutron-deficient nuclei in multinucleon transfer reactions are much larger than those measured in the fragmentation and fusion-evaporation reactions. Several new neutron-deficient nuclei can be produced in the 106 Cd+^112 Sn reaction. The corresponding production cross sections for the new neutron-deficient nuclei,101,112 Sb,103 Te,and 106,107) I,are 2.0 nb,4.1 nb,6.5 nb,0.4 μb and 1.0 μb,respectively.
文摘The future experimental campaign with the SAMURAI setup at RIKEN will explore a wide range of neutron-deficient nuclei with a particular focus on the most critical(p, γ) reaction rates relevant to the astrophysical rp-process in type-I X-ray bursts(XRB). Intense radioactive-ion(RI) beams at an energy of a few hundred Me V/nucleon will be deployed to populate proton-unbound states in the nuclei of interest through the Coulomb excitation or nucleon-removal processes. The decay of these states into a proton and a heavy residue will be measured using complete kinematics and the information about time reversal proton-capture process will be obtained. This method will provide the vital experimental data on the resonances, which dominate the stellar(p, γ) reaction rates, as well as on the direct proton-capture process for some other cases. The experimental setup will utilize for the first time the High-Resolution90?-mode of the SAMURAI spectrometer in combination with the existing detection systems, including custom-designed Si-strip detectors for simultaneous detection and tracking of heavy ions and protons emitted from the target. The details of the experimental method and the utilized apparatus are discussed in this paper.
基金Swedish Research Council(VR)(621-2012-3805,621-2013-4323)Gran Gustafsson Foundation
文摘In this contribution I would like to review briefly our recent studies on nuclear α formation probabilities in heavy nuclei and their indication on the underlying structure of the nuclei involved.In particular, I will show that the empirical α-formation probabilities, which can be extracted from experimental half-lives, exhibit a rather smooth function with changing proton or neutron numbers. This allows us to distinguish the role played by pairing collectivity in the clustering process. The sudden hindrance of the clustering of the nucleons around the N = 126 shell closure is due to the fact that the configuration space does not allow a proper manifestation of the pairing collectivity. The influence of the Z = 82 shell closure on the α formation properties will also be discussed. Moreover, we have evaluated the α-decay fine structure to excited 0+states in Hg and Rn isotopes as well as the α-decay from the excited 0+states in the mother nucleus. It is thus found that the α decay is sensitive to the mixture of configurations corresponding to different nuclear shapes.
基金Supported by National Key Basic Research Program of China(2013CB83440)''National Natural Science Foundation of China(11235001,11320101004)
文摘Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0＋ states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes （except the ground state of 72Kr）, the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.
基金Supported by the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology(NLK2020-02)the National Natural Science Foundation of China(11875328,12075327)the Fundamental Research Funds for the Central Universities,Sun Yat-Sen University(22qntd1801)。
文摘Many isotopes of Np,Pu,Am,and Cm around the N=126 shell still have not been produced in the laboratory.This study aims to investigate the cross sections and yields of the neutron-deficient nuclei of Np,Pu,Am,and Cm produced in the proton-induced spallations of transuranium elements.The isospin-dependent quantum molecular dynamics(IQMD)model is applied to study the dynamical process of reaction,and the subsequent decay process is simulated by the GEMINI++model.The IQMD-GEMINI++model is applied to calculate the cross section,kinetic energy,and angular distribution of the isotopic productions around N=126.The Lindhand,Scharff,and Schiott theory is applied to calculate the energy loss of different heavy nuclei in the target material.A comparison between the data and the calculations shows that the IQMD-GEMINI++model can reproduce the production cross sections of the neutron-deficient nuclei in spallation within approximately 1.5 orders of magnitude.The maximum cross section of the undiscovered isotopes of Np,Pu,Am,and Cm is about 10-5 mb,while the kinetic energies of the productions are all less than 16 MeV.The angular distribution shows that the emission direction of production is mostly at a backward angle.The range of production in the target is within the range of 10-7to 10-5cm.This range is the effective target thickness for the online identification of undiscovered isotopes.Based on the effective thickness of the target and assuming an intensity of 120μA for the proton beam,the yields of the undiscovered neutron-deficient nuclei are calculated.Productions of the undiscovered isotopes of Np,Pu,Am,and Cm by the proton-induced spallations of transuranium elements are feasible.However,experimental techniques for online identification of neutron-deficient nuclei produced in proton-induced spallation should be developed.
文摘Nuclei in the light actinide region with Z 92，N 134 are predicted to be candidates for shape coexistence[1],some nuclei in this region are also predicted to have stable octupole deformation[2]. Actinide nuclei with N=134have been produced up to plutonium (228Pu), and the lightest plutonium isotope and neptunium isotope discoveredso far are 228Pu and 225Np respectively. A campaign has been started to investigate the nuclei in this region. Thereaction 20Ne + 209Bi was used to produce 224Np (N=131) in fusion-evaporation reaction as the first step.
基金Supported by the National Natural Science Foundation of China(11705055)Hunan Provincial Natural Science Foundation of China(2018JJ3324)Excellent Youth Fund of Hunan Provincial Education Department(17B154)
文摘This study investigates the optimal projectile/target combination for the production of new neutron-deficient isotopes of superheavy nuclei(SHN). To this end, the dependence of the evaporation residue cross-section(ERCS) used to synthesize SHN on the mass asymmetry and the isospin of colliding nuclei are analyzed within the dinuclear system(DNS) concept. The predicted ERCSs for the production of new neutron-deficient isotopes of SHN were found to be quite large with the ^(36) S projectile, and the cross-section of SHN decreases slowly with the charge of compound nuclei owing to the increase in their survival probability,. Wsur is not canceled by the decreasing probability, PCN, that the system will evolve from a touching configuration to the compound nucleus in competition with the quasifission process.
基金Supported by National Natural Science Foundation of China(U1632137)
文摘The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected by the DIAMANT CsI ball,Neutron Wall,and the EXOGAM Ge clover array,respectively.In addition to the previously reported levels in 91Ru,new low-to-medium spin states were observed.Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91 Ru.The low-spin states of 91 Ru exhibit a scheme of multi-quasiparticle excitations,which is very similar to that of the neighboring N=47 isotone.These excitations have been interpreted in terms of the shell model.The calculations performed in the configuration space(p3/2,f5/2,p1/2,g9/2)reproduce the experimental excitation energies reasonably well,supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurationsπ(g9/2)^-2v(g9/2^-1 and v(g9/2)^-3.
基金Supported by the National Natural Scie-nce Foundation of China and the Nuclear
文摘The structures of the neutron deficient Nd isotopes of A=128～140 are studied in a schematic hamiltonian in the interacting boson model. The level structure and E2 transitions can be well described in the scheme. In particular, the backbending in the ground state band is well reproduced.
