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 reactions of ^16O＋^204pb, ^82Se＋^138Ba and ^96Zr＋^124Sn lead to the same compound nucleus ^220Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted ...The reactions of ^16O＋^204pb, ^82Se＋^138Ba and ^96Zr＋^124Sn lead to the same compound nucleus ^220Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted the fusion hindrance factor from the evaporation residue cross sections for the reactions of ^82Se＋^138 Ba and ^96Zr＋^124Sn and compared with the results calculated using a two-parameter Smoluchowski equation. The theoretical predictions are basically in agreement with the experimental data. It is found that the probability of forming a compact ^220Th is less than 10% for the reactions considered. For the systems more massive than ^220Th, fusion should be much more strongly suppressed due to the competition of quasifission with complete fusion. Understanding of this inhibition is essential to forming new superheavy nuclei.展开更多
By taking the BUU model, we simulate the superheavy element synthesis reaction. With the rotation effect being included in the BUU model, the effect of the non-centrality of the reaction ^48Ca＋^238U→^286 112 is stud...By taking the BUU model, we simulate the superheavy element synthesis reaction. With the rotation effect being included in the BUU model, the effect of the non-centrality of the reaction ^48Ca＋^238U→^286 112 is studied. It is shown that the promising impact parameter in the synthesis process can be released from zero to a value little smaller than the radius of the smaller nucleus involved in the reaction. Meanwhile, the compound nucleus may involve rich shape phases.展开更多
The capture and fission analysis of heavy ion induced fusion reactions leading to the formation of Z=107-111 superheavy nuclei has been carried out.Attempts have been made to analyze the synthesis traits,such as excit...The capture and fission analysis of heavy ion induced fusion reactions leading to the formation of Z=107-111 superheavy nuclei has been carried out.Attempts have been made to analyze the synthesis traits,such as excitation functions,formation probabilities,barrier characteristics etc.The l-summed Wong model provides a decent description of available data on capture(σCap)and fusion-fission(σff)cross-sections and hence is exploited to make relevant predictions for future experiments.The capture and fusion-fission excitation functions are predicted for the least explored region of superheavy nuclei(SHN)i.e.Z=107-111.The role of massasymmetry(η),Coulomb factor(ZPZT)deformation and orientations,Businari-Gallone massasymmetry(αBG)fission barrier(Bf)etc is duly explored.The present study concludes that the mass-asymmetric reactions involving 24Mg,30Si,and 36S projectiles are preferred for the synthesis of unknown isotopes of Z=107-111.Alternatively,the doubly magic 48Ca-projectile also provides a competing alternative to produce neutron-rich isotopes of the abovementioned SHN.展开更多
The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are d...The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are decomposed into fusion-fission, quasi-fission and fast fission contributions by the dinuclear system (DNS) model. The hindrance to completing fusion both at small and large collision energies is explained. The fusion excitation functions of 32S+90,96Zr in an energy range from above to below the Coulomb barrier are measured and analyzed within a semi-classical model. The obvious effect of positive Q-value multi-neutron transfers on the sub-barrier fusion enhancement is observed in the 32S+96Zr system. In addition, the excitation functions of quasi-elastic scattering at a backward angle have been measured with high precision for the systems of 16O+208Pb, 196Pt, 184W, and 154,152Sm at energies well below the Coulomb barrier. Considering the deformed coupling effects, the extracted diffuseness parameters are close to the values extracted from the systematic analysis of elastic and inelastic scattering data. The elastic scattering angular distribution of 17F+12C at 60 MeV is measured and calculated by using the continuum-discretized coupled-channels (CDCC) approach. It is found that the diffuseness parameter of the real part of core-target potential has to be increased by 20% to reproduce the experimental result, which corresponds to an increment of potential depth at the surface re gion. The breakup cross section and the coupling between breakup and elastic scattering are small.展开更多
In this paper, we show that a theorem concerning the equicontinuity of theoperators in F-spaces can be generalized to a class of operators defined on the binaryfissionable topological groups.
High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are ...High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are identified. The one-phonon γ-band is expanded and a band head level of the two-phonon γ- band is proposed. The systematic characteristics of yrast bands, one-phonon γ-bands, two-phonon γ-bands and quasi-particle bands in 102Mo, 104Mo and 106Mo are discussed.展开更多
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 the National Natural Science Foundation of China under Grants Nos 10235020 and 10235030.
文摘The reactions of ^16O＋^204pb, ^82Se＋^138Ba and ^96Zr＋^124Sn lead to the same compound nucleus ^220Th. In terms of the assumption that the surviving probability is independent of entrance channel, we have extracted the fusion hindrance factor from the evaporation residue cross sections for the reactions of ^82Se＋^138 Ba and ^96Zr＋^124Sn and compared with the results calculated using a two-parameter Smoluchowski equation. The theoretical predictions are basically in agreement with the experimental data. It is found that the probability of forming a compact ^220Th is less than 10% for the reactions considered. For the systems more massive than ^220Th, fusion should be much more strongly suppressed due to the competition of quasifission with complete fusion. Understanding of this inhibition is essential to forming new superheavy nuclei.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10425521, 10075002, and 10135030, the Major State Basic Research Development Programme under Grant No G2000077400, and Doctoral Program Foundation of the Ministry of Education of China under Grant No 20040001010, the Foundation for University Key Teacher by the Ministry of Education of China.
文摘By taking the BUU model, we simulate the superheavy element synthesis reaction. With the rotation effect being included in the BUU model, the effect of the non-centrality of the reaction ^48Ca＋^238U→^286 112 is studied. It is shown that the promising impact parameter in the synthesis process can be released from zero to a value little smaller than the radius of the smaller nucleus involved in the reaction. Meanwhile, the compound nucleus may involve rich shape phases.
基金financial support from the UGC-DAE Consortium for Scientific Research,F.No.UGC-DAE-CSR-KC/CRS/19/NP09/0920the INSPIRE-fellowship(grant no.DST/INSPIRE/03/2015/000199).
文摘The capture and fission analysis of heavy ion induced fusion reactions leading to the formation of Z=107-111 superheavy nuclei has been carried out.Attempts have been made to analyze the synthesis traits,such as excitation functions,formation probabilities,barrier characteristics etc.The l-summed Wong model provides a decent description of available data on capture(σCap)and fusion-fission(σff)cross-sections and hence is exploited to make relevant predictions for future experiments.The capture and fusion-fission excitation functions are predicted for the least explored region of superheavy nuclei(SHN)i.e.Z=107-111.The role of massasymmetry(η),Coulomb factor(ZPZT)deformation and orientations,Businari-Gallone massasymmetry(αBG)fission barrier(Bf)etc is duly explored.The present study concludes that the mass-asymmetric reactions involving 24Mg,30Si,and 36S projectiles are preferred for the synthesis of unknown isotopes of Z=107-111.Alternatively,the doubly magic 48Ca-projectile also provides a competing alternative to produce neutron-rich isotopes of the abovementioned SHN.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10575134, 10675169 and 10735100)the Major State Basic Research Developing Program (Grant No. 2007CB815003)
文摘The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are decomposed into fusion-fission, quasi-fission and fast fission contributions by the dinuclear system (DNS) model. The hindrance to completing fusion both at small and large collision energies is explained. The fusion excitation functions of 32S+90,96Zr in an energy range from above to below the Coulomb barrier are measured and analyzed within a semi-classical model. The obvious effect of positive Q-value multi-neutron transfers on the sub-barrier fusion enhancement is observed in the 32S+96Zr system. In addition, the excitation functions of quasi-elastic scattering at a backward angle have been measured with high precision for the systems of 16O+208Pb, 196Pt, 184W, and 154,152Sm at energies well below the Coulomb barrier. Considering the deformed coupling effects, the extracted diffuseness parameters are close to the values extracted from the systematic analysis of elastic and inelastic scattering data. The elastic scattering angular distribution of 17F+12C at 60 MeV is measured and calculated by using the continuum-discretized coupled-channels (CDCC) approach. It is found that the diffuseness parameter of the real part of core-target potential has to be increased by 20% to reproduce the experimental result, which corresponds to an increment of potential depth at the surface re gion. The breakup cross section and the coupling between breakup and elastic scattering are small.
文摘In this paper, we show that a theorem concerning the equicontinuity of theoperators in F-spaces can be generalized to a class of operators defined on the binaryfissionable topological groups.
基金Supported by National Natural Science Foundation of China (10575057, 10775078)Major State Basic Research Development Program (2007CB815005)+1 种基金Special Program of Higher Education Science Foundation (20070003149)U.S. Department of Energy under Grant and Contract Nos. DE-FG05-88ER40407, DE-AC03-76SF00098
文摘High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are identified. The one-phonon γ-band is expanded and a band head level of the two-phonon γ- band is proposed. The systematic characteristics of yrast bands, one-phonon γ-bands, two-phonon γ-bands and quasi-particle bands in 102Mo, 104Mo and 106Mo are discussed.
