The nucleon-nucleon interaction is investigated by using the improved quantum molecular dynamic （ImQMD） model with three sets of parameters IQ1, IQ2 and IQ3, in which the corresponding incompressibility coefficients...The nucleon-nucleon interaction is investigated by using the improved quantum molecular dynamic （ImQMD） model with three sets of parameters IQ1, IQ2 and IQ3, in which the corresponding incompressibility coefficients of nuclear matter are different. The charge distributions of fragments are calculated for various reaction systems at different incident energies. The parameters strongly affect the charge distributions and the fragment multiplicity spectrum below the threshold energy of nuclear multifragmentation. The fragment multiplicity spectrum for 238U＋197Au at 15 A MeV and the charge distributions for 129Xe＋12~Sn at 32 and 45 A MeV, and 197Au＋197Au at 35 A MeV are reproduced by the ImQMD model with the set of parameter IQ3. It is found that： 1） The charge distribution of the fragments and the fragment multiplicity spectrum are good observables for testing the model and the parameters. 2） The Fermi energy region is a sensitive energy region for studying nucleon-nucleon interaction.展开更多
The improved quantum molecular dynamics model was employed to study the ^(238)U+^(238)U multinucleon transfer reaction at E_(c.m.)=833 Me V in this work.The influence of the orientation effect on the nuclear deformati...The improved quantum molecular dynamics model was employed to study the ^(238)U+^(238)U multinucleon transfer reaction at E_(c.m.)=833 Me V in this work.The influence of the orientation effect on the nuclear deformation at the contact moment,the composite system lifetime,the transfer rate and the fragment production mechanism are investigated.Statistical analysis reveals that at the contact moment,the orientation of the projectile and the target have less influence on each other and retain their respective initial characteristics to some extent.For collision parameters less than 6 fm,significant differences are observed in composite system lifetime and transfer rate under different orientation configurations;however,the orientation effect gradually diminishes with increasing collision parameters.Additionally,it is found that transfer reactions dominate when the collision parameter b≤6 fm,while elastic and inelastic scattering events increase rapidly as the collision parameter exceeds 6 fm.Within the range of 10≤b≤13 fm,the transfer probability for side–side collisions is significantly higher compared to other cases.展开更多
A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the ...A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables,namely isospin transport ratios,single and double ratios of the yields of neutrons and protons are investigated.The isospin transport ratios are strongly sensitive to the slope of symmetry energy,and are not very sensitive to the nucleon effective mass splitting.On the other hand,the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting.By comparing our calculations with the data,we find that the constrained L value(the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models,and the isospin diffusion data prefer to mn*>mp*,but it is not a strong constraint with deep χ2minimum.展开更多
The main progresses in the multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental progress and theoretical progress, the predicted product...The main progresses in the multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental progress and theoretical progress, the predicted production cross sections for unknown neutron-rich heavy nuclei and the trans-uranium nuclei are presented.展开更多
Some nearly-symmetric fusion reactions are systematically investigated with the improved quantum molecular dynamics(Im QMD)model. By introducing two-body inelastic scattering in the Fermi constraint procedure, the sta...Some nearly-symmetric fusion reactions are systematically investigated with the improved quantum molecular dynamics(Im QMD)model. By introducing two-body inelastic scattering in the Fermi constraint procedure, the stability of an individual nucleus and the description of fusion cross sections at energies near the Coulomb barrier can be further improved. Simultaneously, the quasifission process in154Sm+160Gd is also investigated with the microscopic dynamics model for the first time. We find that at energies above the Bass barrier, the fusion probability is smaller than 10-5for this reaction, and the nuclear contact time is generally smaller than 1500 fm/c. From the central collisions of Sm+Gd, the neutron-rich fragments such as164,165 Gd,192W can be produced in the Im QMD simulations, which implies that the quasi-fission reaction could be an alternative way to synthesize new neutron-rich heavy nuclei.展开更多
The mass number distributions of three fragments from the ternary fission of the system 197Au+197Au are reproduced rather well by using the improved quantum molecular dynamics (ImQMD) model without any adjusting param...The mass number distributions of three fragments from the ternary fission of the system 197Au+197Au are reproduced rather well by using the improved quantum molecular dynamics (ImQMD) model without any adjusting parameter. It is found that the probability of ternary fission evidently depends on the incident energy and the impact parameter, and the two-body dissipation is the main mechanism responsible for the formation of the third fragment with comparable mass.展开更多
The strongly damped collisions of very heavy nuclei ^232Th＋^250Cf at the energy range of 680--1880 MeV have been studied within the improved quantum molecular dynamics model. The production probability of primary sup...The strongly damped collisions of very heavy nuclei ^232Th＋^250Cf at the energy range of 680--1880 MeV have been studied within the improved quantum molecular dynamics model. The production probability of primary superheavy fragments with Z≥ 114 （SHFs） for the asymmetric reaction ^232Th＋^250cf is higher than that for the symmetric reaction ^244Pu＋^244pu and ^238U＋^238U. The calculated results show that the mass and charge distributions of primary fragments, the excitation energy distribution of SHFs depend on the incident energies strongly. Two stages of the decay process of composite systems are distinguished by very different decay slopes, which imply different decay mechanisms of the composite system. The first stage is for the decay of giant composite systems and the second one corresponds to the decay of fragments of giant composite systems including SHFs through emitting neutron, proton or other charged particles, and also through fission or fragmentation. The slow reduction of SHFs in the second stage seems to be helpful for the survival of primary superheavy fragments.展开更多
Strongly damped reactions of 238U+238U, at Ecm = 680—1880 MeV have been studied based on the improved quantum molecular dynamics model. We find that at a certain energy region the entrance channel potential is weakly...Strongly damped reactions of 238U+238U, at Ecm = 680—1880 MeV have been studied based on the improved quantum molecular dynamics model. We find that at a certain energy region the entrance channel potential is weakly repulsive and the dissipation is very strong after touching configuration, these two effects make the time delay of re-separation for colliding system. The single particle potential well of the transiently formed composite system has Coulomb barrier about 15—20 MeV high at the surface, which makes the excited unbound protons being still embedded in the potential well and moving in a common mono-single particle potential for a period of time and thus restrains from quick decay of the composite system.展开更多
基金National Natural Science Foundation of China(11005003,10975095,11275052,11005002)Natural Science Foundation of He’nan Educational Committee(2011A140001,2011GGJS-147)Innovation Fund of Undergraduate at Anyang Normal University(ASCX/2012Z28)
文摘The nucleon-nucleon interaction is investigated by using the improved quantum molecular dynamic （ImQMD） model with three sets of parameters IQ1, IQ2 and IQ3, in which the corresponding incompressibility coefficients of nuclear matter are different. The charge distributions of fragments are calculated for various reaction systems at different incident energies. The parameters strongly affect the charge distributions and the fragment multiplicity spectrum below the threshold energy of nuclear multifragmentation. The fragment multiplicity spectrum for 238U＋197Au at 15 A MeV and the charge distributions for 129Xe＋12~Sn at 32 and 45 A MeV, and 197Au＋197Au at 35 A MeV are reproduced by the ImQMD model with the set of parameter IQ3. It is found that： 1） The charge distribution of the fragments and the fragment multiplicity spectrum are good observables for testing the model and the parameters. 2） The Fermi energy region is a sensitive energy region for studying nucleon-nucleon interaction.
基金supported by the Natural Science Foundation of Guangxi under Grant No.2024GXNSFBA010377,No.2022GXNSFBA035528,No.2023GXNSFBA026008Guangxi Science and Technology Base and Special Talent Program under Grant No.Guike AD22035060+2 种基金the Central Government Guides Local Scientific and Technological Development Fund Projects under Grant No.Guike ZY22096024the National Natural Science Foundation of China under Grant No.12135004,No.11635003 No.11961141004,No.12365016the Innovation Project of Guangxi Graduate Education Grant No.YCBZ2023060.
文摘The improved quantum molecular dynamics model was employed to study the ^(238)U+^(238)U multinucleon transfer reaction at E_(c.m.)=833 Me V in this work.The influence of the orientation effect on the nuclear deformation at the contact moment,the composite system lifetime,the transfer rate and the fragment production mechanism are investigated.Statistical analysis reveals that at the contact moment,the orientation of the projectile and the target have less influence on each other and retain their respective initial characteristics to some extent.For collision parameters less than 6 fm,significant differences are observed in composite system lifetime and transfer rate under different orientation configurations;however,the orientation effect gradually diminishes with increasing collision parameters.Additionally,it is found that transfer reactions dominate when the collision parameter b≤6 fm,while elastic and inelastic scattering events increase rapidly as the collision parameter exceeds 6 fm.Within the range of 10≤b≤13 fm,the transfer probability for side–side collisions is significantly higher compared to other cases.
基金Supported by National Natural Science Foundation of China(NSFC) projects (Nos.11075215,10875031,11005022,11005155 and 11275052)973 Program of China(No.2013CB834404)National Science Foundation(Grants No.PHY-0606007)
文摘A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables,namely isospin transport ratios,single and double ratios of the yields of neutrons and protons are investigated.The isospin transport ratios are strongly sensitive to the slope of symmetry energy,and are not very sensitive to the nucleon effective mass splitting.On the other hand,the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting.By comparing our calculations with the data,we find that the constrained L value(the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models,and the isospin diffusion data prefer to mn*>mp*,but it is not a strong constraint with deep χ2minimum.
文摘The main progresses in the multinucleon transfer reactions at energies close to the Coulomb barrier are reviewed. After a short presentation of the experimental progress and theoretical progress, the predicted production cross sections for unknown neutron-rich heavy nuclei and the trans-uranium nuclei are presented.
基金supported by the National Natural Science Foundation of China(Grant Nos.11422548,11275052,11365005 and 11375062)the Open Project Program of State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,China(Grant No.Y4KF041CJ1)
文摘Some nearly-symmetric fusion reactions are systematically investigated with the improved quantum molecular dynamics(Im QMD)model. By introducing two-body inelastic scattering in the Fermi constraint procedure, the stability of an individual nucleus and the description of fusion cross sections at energies near the Coulomb barrier can be further improved. Simultaneously, the quasifission process in154Sm+160Gd is also investigated with the microscopic dynamics model for the first time. We find that at energies above the Bass barrier, the fusion probability is smaller than 10-5for this reaction, and the nuclear contact time is generally smaller than 1500 fm/c. From the central collisions of Sm+Gd, the neutron-rich fragments such as164,165 Gd,192W can be produced in the Im QMD simulations, which implies that the quasi-fission reaction could be an alternative way to synthesize new neutron-rich heavy nuclei.
基金Supported by National Natural Science Foundation of China (10475008, 10435020, 10235030, 10675172)Scientific Research Foundation for Returned Overseas Chinese Scholars, Ministry of Personnel and Ministry of Education of China (MOP2006138,MOE2005383)National Basic Research program of China (2007CB209900) and HSCC of Beijing Normal University
文摘The mass number distributions of three fragments from the ternary fission of the system 197Au+197Au are reproduced rather well by using the improved quantum molecular dynamics (ImQMD) model without any adjusting parameter. It is found that the probability of ternary fission evidently depends on the incident energy and the impact parameter, and the two-body dissipation is the main mechanism responsible for the formation of the third fragment with comparable mass.
基金Supported by National Natural Science Foundation of China(10675127,10235030,10235020)
文摘The strongly damped collisions of very heavy nuclei ^232Th＋^250Cf at the energy range of 680--1880 MeV have been studied within the improved quantum molecular dynamics model. The production probability of primary superheavy fragments with Z≥ 114 （SHFs） for the asymmetric reaction ^232Th＋^250cf is higher than that for the symmetric reaction ^244Pu＋^244pu and ^238U＋^238U. The calculated results show that the mass and charge distributions of primary fragments, the excitation energy distribution of SHFs depend on the incident energies strongly. Two stages of the decay process of composite systems are distinguished by very different decay slopes, which imply different decay mechanisms of the composite system. The first stage is for the decay of giant composite systems and the second one corresponds to the decay of fragments of giant composite systems including SHFs through emitting neutron, proton or other charged particles, and also through fission or fragmentation. The slow reduction of SHFs in the second stage seems to be helpful for the survival of primary superheavy fragments.
基金Supported by National Natural Science Foundation of China (10235030, 10675172)National Basic Research Program of China (2007CB209900)
文摘Strongly damped reactions of 238U+238U, at Ecm = 680—1880 MeV have been studied based on the improved quantum molecular dynamics model. We find that at a certain energy region the entrance channel potential is weakly repulsive and the dissipation is very strong after touching configuration, these two effects make the time delay of re-separation for colliding system. The single particle potential well of the transiently formed composite system has Coulomb barrier about 15—20 MeV high at the surface, which makes the excited unbound protons being still embedded in the potential well and moving in a common mono-single particle potential for a period of time and thus restrains from quick decay of the composite system.
