In this study,we investigated the isospin properties of intermediate mass fragments(IMFs)for the central collisions of^(112,124)Sn+^(112,124)Sn at a beam energy of50 MeV per nucleon using an improved quantum molecular...In this study,we investigated the isospin properties of intermediate mass fragments(IMFs)for the central collisions of^(112,124)Sn+^(112,124)Sn at a beam energy of50 MeV per nucleon using an improved quantum molecular dynamics model(ImQMD)coupled with a sequential decay model(GEMINI).Three observables were analyzed:(1)the average center-of-mass kinetic energy per nucleon<Ec.m./A>of fragments as a function of their charge number Z;(2)the average neutron number to proton number ratio(<N>/Z)of fragments with a given charge number Z as a function of their center-of-mass kinetic energy per nucleon(Ec.m./A);and(3)the average total neutron number to total proton number ratio(ΣN/ΣZ)and double ratio(DR(N/Z))of IMFs with Z=3-8 as a function of their center-of-mass kinetic energy per nucleon Ec.m./A.Our calculations revealed that the sensitivity of the isospin properties of IMFs relative to the stiffness of the symmetry energy remains even after sequential decay.By comparing the calculations ofΣN/ΣZ and DR(N/Z)with the data,it was found that the soft symmetry energy,i.e.,γ=0.5,is favored.展开更多
Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the iso...Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the isospin emission in heavy-ion collisions is investigated thoroughly.It is found that the yield ratios of energetic neutrons to protons squeezed out during the compression stage of two colliding nuclides are sensitive to the isospin splitting.The elliptic flows of free nucleons are also to be promising observables for extracting the nucleon effective mass splitting.Further experimental measurements are being expected,in particular at the CSR-CEE platform in Lanzhou.Several observables are proposed for constraining the density dependence of symmetry energy,such as the transverse flow difference of neutrons and protons,double ratios of n/p and π-/π+,excitation functions of π-/π+ and K0/K+.展开更多
The isospin effects of projectile fragmentation at intermediate energies are investigated using an isospin-dependent Boltzmann-Langevin model.The collisions of mass-symmetric reactions including 58Fe,58Ni+58Fe,and Ni ...The isospin effects of projectile fragmentation at intermediate energies are investigated using an isospin-dependent Boltzmann-Langevin model.The collisions of mass-symmetric reactions including 58Fe,58Ni+58Fe,and Ni at intermediate energies,in the 30 to 100 MeV/A range,are studied for different symmetry energies.Yield ratios of the isotopic,isobaric,and isotonic pairs of fragments from the intermediate-mass region using three symmetry energies are extracted as functions of the N/Z ratio of the composite systems in the entrance channel and the incident energies.It is found that the yield ratios are sensitive to symmetry energies,especially for neutron-rich systems,and the calculations using soft symmetry energy are closer to the experimental data.The isospin effect is stronger for the soft symmetry energy,owing to the competition of the repulsive Coulomb force and the symmetry energy attractive force on the proton.For the first time,the splits are presented,revealing a transition from the isospin equilibrium at lower energies to translucency at intermediate energies.The results show a degree of transparency in that intermediate mass fragments undergo a transition from dependence on the composite systems in the entrance channel to reliance on the projectile and target nuclei.展开更多
We improve the isospin dependent quantum molecular dynamical model by including isospin effects in the Skyrme potential and the momentum dependent interaction to obtain an isospin dependent Skyrme potential and an iso...We improve the isospin dependent quantum molecular dynamical model by including isospin effects in the Skyrme potential and the momentum dependent interaction to obtain an isospin dependent Skyrme potential and an isospin dependent momentum interaction. We investigate the isospin effects of Skyrme potential and momentum dependent interaction on the isospin fractionation ratio and the dynamical mechanism in intermediate energy heavy ion collisions. It is found that the isospin dependent Skyrme potential and the isospin dependent momentum interaction produce some important isospin effects in the isospin fractionation ratio.展开更多
Using relativistic mean field theory, the neutron and the proton density distribution of 56Ni nuclei could be obtained in the ground state and the excited state. Based on the framework of the quantum molecular dynamic...Using relativistic mean field theory, the neutron and the proton density distribution of 56Ni nuclei could be obtained in the ground state and the excited state. Based on the framework of the quantum molecular dynamics model, the 56Ni nuclei have been simulated in ground state and in the neutron or proton excited state. We then used the three different states of 56Ni to collide with the 56Ni in the ground state. To discuss the evolution of the nuclear stopping in different reactions, two kinds of different excited nuclear reactions were studied at different reaction energies and at different impact parameters. Studies have shown that the nuclear stopping of an excited nuclear reaction is sensitive to the isospin-dependent in-medium nucleon-nucleon cross section, compared with the response value of the ground state nuclear reaction. So, it is better for the excited nuclei to extract the isospin dependence of nucleon-nucleon cross section information.展开更多
Probing in-medium nucleon-nucleon （NN） cross section σ1/NN（α） in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics （IQMD） with the isospin- and momentum-de...Probing in-medium nucleon-nucleon （NN） cross section σ1/NN（α） in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics （IQMD） with the isospin- and momentum-dependent interaction （IMDI（T））. It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN（α） in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN（α） in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R＇s in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN（α） because of adding a new judgement.展开更多
Isospin effects on particle emission of fissioning isobaric sources and isotopic sources , and its dependence on the excitation energy are studied via Smoluchowski equations. It is shown that with increasing the isos...Isospin effects on particle emission of fissioning isobaric sources and isotopic sources , and its dependence on the excitation energy are studied via Smoluchowski equations. It is shown that with increasing the isospin of fissioning systems, charged-particle emission is not sensitive to the strength of nuclear dissipation. In addition, we have found that increasing the excitation energy not only increases the influence of nuclear dissipation on particle emission but also greatly enhances the sensitivity of the emission of pre-scission neutrons or charged particles to the isospin of the system. Therefore, in order to extract dissipation strength more accurately by taking light particle multiplicities it is important to choose both a highly excited compound nucleus and a proper kind of particles for systems with different isospins.展开更多
An isospin-dependent quantum molecular dynamical model （IQMD） is developed, with the isospin degree of freedom in the momentum-dependent interaction（MDI） included in IQMD, to obtain an isospin- and momentum-depend...An isospin-dependent quantum molecular dynamical model （IQMD） is developed, with the isospin degree of freedom in the momentum-dependent interaction（MDI） included in IQMD, to obtain an isospin- and momentum-dependent interaction （IMDI） in IQMD. We investigate the effect of IMDI on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the IMDI induces the significant reductions in the isospin fractionation ratio for all of beam energies, impact parameters, neutron-proton ratios and mass number of colliding systems. However, the strong dependence of isospin fractionation ratio on the symmetrical potential is preserved, with the isospin degree of freedom included in the MDI, i.e. the isospin fractionation ratio is still a good probe for extracting the information about the equation of state of isospin asymmetrical nuclear matter.展开更多
The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical...The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical decay model. The magnitude of this excess for a low-isospin fissioning nucleus is shown to be larger and its dependence on the nuclear viscosity coefficient to be stronger than those of a high-isospin fissioning nucleus. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, we had better choose those compound systems with small isospin.展开更多
Heavy-ion fusion reactions are relevant to numerous important issues in the stellar environment as well as in the synthesis of new nuclides and superheavy elements. In this study, the role of Pauli blocking and the is...Heavy-ion fusion reactions are relevant to numerous important issues in the stellar environment as well as in the synthesis of new nuclides and superheavy elements. In this study, the role of Pauli blocking and the isospin effect in sub-barrier fusion reactions is investigated using the well established coupled-channel method. An isospindependent Pauli blocking potential is proposed to better address the deep sub-barrier fusion hindrance problem. We find that the Pauli blocking effect manifests itself strongly for isospin symmetric targets and is reduced for targets with large isospin asymmetries. The agreement between experimental and theoretical fusion cross sections is improved for both the ^(12)C-target and ^(16)O-target systems.展开更多
Using a diffusion model we investigate deformation effects on the sensitivity of different light particles to nuclear dissipation for a rather neutron-deficlent ^178Pb system. Galculations show that deformation signif...Using a diffusion model we investigate deformation effects on the sensitivity of different light particles to nuclear dissipation for a rather neutron-deficlent ^178Pb system. Galculations show that deformation significantly increases the sensitivity of neutron emission to dissipation strength, and that this effect becomes stronger with increasing deformation.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11875323,11705163,11790320,11790323,and11961141003)the National Key R&D Program of China(No.2018YFA0404404)+1 种基金the Continuous Basic Scientific Research Project(Nos.WDJC-2019-13,BJ20002501)funding from the China Institute of Atomic Energy and the Leading Innovation Project of CNNC(Nos.LC192209000701 and LC202309000201)。
文摘In this study,we investigated the isospin properties of intermediate mass fragments(IMFs)for the central collisions of^(112,124)Sn+^(112,124)Sn at a beam energy of50 MeV per nucleon using an improved quantum molecular dynamics model(ImQMD)coupled with a sequential decay model(GEMINI).Three observables were analyzed:(1)the average center-of-mass kinetic energy per nucleon<Ec.m./A>of fragments as a function of their charge number Z;(2)the average neutron number to proton number ratio(<N>/Z)of fragments with a given charge number Z as a function of their center-of-mass kinetic energy per nucleon(Ec.m./A);and(3)the average total neutron number to total proton number ratio(ΣN/ΣZ)and double ratio(DR(N/Z))of IMFs with Z=3-8 as a function of their center-of-mass kinetic energy per nucleon Ec.m./A.Our calculations revealed that the sensitivity of the isospin properties of IMFs relative to the stiffness of the symmetry energy remains even after sequential decay.By comparing the calculations ofΣN/ΣZ and DR(N/Z)with the data,it was found that the soft symmetry energy,i.e.,γ=0.5,is favored.
基金Supported by National Natural Science Foundation of China(NSFC) projects (No.11175218)the Advancement Society of Young Innovation of Chinese Academy of Sciences
文摘Two different isospin splittings of nucleon effective mass in nuclear medium as the form of mn*>mp* and mn*<mp* have been implemented in an isospin and momentum dependent transport model.Their impacts on the isospin emission in heavy-ion collisions is investigated thoroughly.It is found that the yield ratios of energetic neutrons to protons squeezed out during the compression stage of two colliding nuclides are sensitive to the isospin splitting.The elliptic flows of free nucleons are also to be promising observables for extracting the nucleon effective mass splitting.Further experimental measurements are being expected,in particular at the CSR-CEE platform in Lanzhou.Several observables are proposed for constraining the density dependence of symmetry energy,such as the transverse flow difference of neutrons and protons,double ratios of n/p and π-/π+,excitation functions of π-/π+ and K0/K+.
基金Supported by the National Natural Science Foundation of China(11635003,11025524,11161130520)National Basic Research Program of China(2010CB832903)the European Commissions 7th Framework Programme(FP7-PEOPLE-2010-IRSES)under Grant Agreement Project(269131)。
文摘The isospin effects of projectile fragmentation at intermediate energies are investigated using an isospin-dependent Boltzmann-Langevin model.The collisions of mass-symmetric reactions including 58Fe,58Ni+58Fe,and Ni at intermediate energies,in the 30 to 100 MeV/A range,are studied for different symmetry energies.Yield ratios of the isotopic,isobaric,and isotonic pairs of fragments from the intermediate-mass region using three symmetry energies are extracted as functions of the N/Z ratio of the composite systems in the entrance channel and the incident energies.It is found that the yield ratios are sensitive to symmetry energies,especially for neutron-rich systems,and the calculations using soft symmetry energy are closer to the experimental data.The isospin effect is stronger for the soft symmetry energy,owing to the competition of the repulsive Coulomb force and the symmetry energy attractive force on the proton.For the first time,the splits are presented,revealing a transition from the isospin equilibrium at lower energies to translucency at intermediate energies.The results show a degree of transparency in that intermediate mass fragments undergo a transition from dependence on the composite systems in the entrance channel to reliance on the projectile and target nuclei.
基金Supported by National Natural Science Foundation of China(10435080,10447006,10575075)CAS Knowledge Innovation Project(KJCX2-SW-N02)+2 种基金Major State Basic Research Development Program in China(G2000077400)the Scientific Research Funds for the Doctor,University of Shanghai for Science and Technologythe Science and Technological Fund of Shanghai Municipal Education Commission for Selecting and Cultivating Excellent University Young Teachers
文摘We improve the isospin dependent quantum molecular dynamical model by including isospin effects in the Skyrme potential and the momentum dependent interaction to obtain an isospin dependent Skyrme potential and an isospin dependent momentum interaction. We investigate the isospin effects of Skyrme potential and momentum dependent interaction on the isospin fractionation ratio and the dynamical mechanism in intermediate energy heavy ion collisions. It is found that the isospin dependent Skyrme potential and the isospin dependent momentum interaction produce some important isospin effects in the isospin fractionation ratio.
基金Supported by National Natural Science Foundation of China(10905041)Innovation Fund Project for Graduate Students of Shanghai(JWCXSL1202)China Scholarship Council Foundation(201208310156)
文摘Using relativistic mean field theory, the neutron and the proton density distribution of 56Ni nuclei could be obtained in the ground state and the excited state. Based on the framework of the quantum molecular dynamics model, the 56Ni nuclei have been simulated in ground state and in the neutron or proton excited state. We then used the three different states of 56Ni to collide with the 56Ni in the ground state. To discuss the evolution of the nuclear stopping in different reactions, two kinds of different excited nuclear reactions were studied at different reaction energies and at different impact parameters. Studies have shown that the nuclear stopping of an excited nuclear reaction is sensitive to the isospin-dependent in-medium nucleon-nucleon cross section, compared with the response value of the ground state nuclear reaction. So, it is better for the excited nuclei to extract the isospin dependence of nucleon-nucleon cross section information.
基金Project supported by the State Key Development Program for Basic Research of China （Grant No G2000077400）, the Major Program of the National Natural Science Foundation of China （Grant Nos 10435080 and 105350101）, the National Natural Science Foundation of China （Grant Nos 10447006 and 10575075）, the CAS Knowledge Innovation Project Program （Grant No KJCX2-SW-N02）.
文摘Probing in-medium nucleon-nucleon （NN） cross section σ1/NN（α） in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics （IQMD） with the isospin- and momentum-dependent interaction （IMDI（T））. It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping R on the in-medium NN cross section α1/NN（α） in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of σ1/NN（α） in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R＇s in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of σ1/NN（α） because of adding a new judgement.
基金the Teaching ＆ Researching Foundation for Outstanding Teachers of Southeast University
文摘Isospin effects on particle emission of fissioning isobaric sources and isotopic sources , and its dependence on the excitation energy are studied via Smoluchowski equations. It is shown that with increasing the isospin of fissioning systems, charged-particle emission is not sensitive to the strength of nuclear dissipation. In addition, we have found that increasing the excitation energy not only increases the influence of nuclear dissipation on particle emission but also greatly enhances the sensitivity of the emission of pre-scission neutrons or charged particles to the isospin of the system. Therefore, in order to extract dissipation strength more accurately by taking light particle multiplicities it is important to choose both a highly excited compound nucleus and a proper kind of particles for systems with different isospins.
基金Project supported by the State Key Program of Basic Research of China（Grant No G2000077400）, the Major program of the National Natural Science Foundation of China （Grant Nos 10435080 and 105350101）, the National Natural Science Foundation of China （Grant Nos 10447006, 10575075, 10125521 and 10447113）, the Knowledge Innovation Program of the Chinese Academy of Sciences （Grant No KJCX2-SW-N02）, Jiangsu Planned Projects for Postdoctoral Research Funds and China Postdoctoral Science Foundation.
文摘An isospin-dependent quantum molecular dynamical model （IQMD） is developed, with the isospin degree of freedom in the momentum-dependent interaction（MDI） included in IQMD, to obtain an isospin- and momentum-dependent interaction （IMDI） in IQMD. We investigate the effect of IMDI on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the IMDI induces the significant reductions in the isospin fractionation ratio for all of beam energies, impact parameters, neutron-proton ratios and mass number of colliding systems. However, the strong dependence of isospin fractionation ratio on the symmetrical potential is preserved, with the isospin degree of freedom included in the MDI, i.e. the isospin fractionation ratio is still a good probe for extracting the information about the equation of state of isospin asymmetrical nuclear matter.
基金supported by National Natural Science Foundation of China under Grant No.10405007
文摘The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical decay model. The magnitude of this excess for a low-isospin fissioning nucleus is shown to be larger and its dependence on the nuclear viscosity coefficient to be stronger than those of a high-isospin fissioning nucleus. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, we had better choose those compound systems with small isospin.
基金Supported by the National Natural Science Foundation of China (12275129, 12105080)the Fundamental Research Funds for the Central Universities(020414380209)。
文摘Heavy-ion fusion reactions are relevant to numerous important issues in the stellar environment as well as in the synthesis of new nuclides and superheavy elements. In this study, the role of Pauli blocking and the isospin effect in sub-barrier fusion reactions is investigated using the well established coupled-channel method. An isospindependent Pauli blocking potential is proposed to better address the deep sub-barrier fusion hindrance problem. We find that the Pauli blocking effect manifests itself strongly for isospin symmetric targets and is reduced for targets with large isospin asymmetries. The agreement between experimental and theoretical fusion cross sections is improved for both the ^(12)C-target and ^(16)O-target systems.
基金The project supported by National Natural Science Foundation of China under Grant No. 10405007 and the Teaching and Researching Foundation of the Excellent Teacher of Southeast University
文摘Using a diffusion model we investigate deformation effects on the sensitivity of different light particles to nuclear dissipation for a rather neutron-deficlent ^178Pb system. Galculations show that deformation significantly increases the sensitivity of neutron emission to dissipation strength, and that this effect becomes stronger with increasing deformation.
