The experimental data concerning the58Ni+48Ca reaction at Elab(Ni)=25A MeV,collected by using the CHIMERA 4π device,have been analyzed in order to investigate the competition among different reaction mechanisms for c...The experimental data concerning the58Ni+48Ca reaction at Elab(Ni)=25A MeV,collected by using the CHIMERA 4π device,have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain.As a main criterion for centrality selection we have chosen the flow angle(flow) method,making an event-by-event analysis that considers the shape of events,as it is determined by the eigenvectors of the experimental kinetic-energy tensor.For the selected central events(flow >60°) some global variables,good to characterize the pattern of central collisions have been constructed.The main features of the reaction products were explored by using different constraints on some of the relevant observables,like mass and velocity distributions and their correlations.Much emphasis was devoted,for central collisions,to the competition between fusion-evaporation processes with subsequent identification of a heavy residue and a possible multifragmentation mechanism of a well defined(if any) transient nuclear system.Dynamical evolution of the system and pre-equilibrium emission were taken into account by simulating the reactions in the framework of transport theories.Different approaches have been envisaged(dynamical stochastic BNV calculations + sequential SIMON code,QMD,CoMD,etc.).Preliminary comparison of the experimental data with BNV calculations shows reasonable agreement with the assumption of sequential multifragmentation emission in the mass region of IMFs close to the heavy residues.Possible deviations from sequential processes were found for those IMFs in the region of masses intermediate between the mass of heavy residues and the mass of light IMFs.Further simulations are in progress.The experimental analysis will be enriched also by information obtained inspecting the IMF-IMF correlation function,in order to elucidated the nature of space-time decay property of the emitting source associated with events having the largest IMF multiplicity.展开更多
Near degeneracy between two quantum states is usually associated with fundamental symmetries and symmetry breakings in complex many-body systems like atomic nuclei.Pseudospin symmetry was introduced to describe energy...Near degeneracy between two quantum states is usually associated with fundamental symmetries and symmetry breakings in complex many-body systems like atomic nuclei.Pseudospin symmetry was introduced to describe energy degeneracy between single-particle states with quantum numbers(n,l,j=l+1/2)and(n-1,l+2,j=l+3/2)[1-3].展开更多
Backbending played a pivotal role in the progress of high-spin structure research[1].This phennomenon was interpreted as a result of band-crossing between two intrinsic configurations which dominate lower-and higher-s...Backbending played a pivotal role in the progress of high-spin structure research[1].This phennomenon was interpreted as a result of band-crossing between two intrinsic configurations which dominate lower-and higher-spin region.Usually the two configurations are differed by two nucleons,which are paired in the former,and unpaired in the latter.According to the strong-coupling scheme,two unpaired quasi-particles can couple to both high-K and low-K configurations in deformed nuclei.Usually only the lower can be identified experimentally since it is favoured by the Gallagher-Moszkowski spin-spin coupling rules[2].展开更多
Isomeric I^(π)=8^(-) states have been observed in the even-even N=74 nuclei ^(138)Gd[1],^(136)Sm[2],^(134)Nd[3],^(132)Ce[4],^(130)Ba[5],^(128)Xe[6]with half-lives ranging from nanoseconds(Xe)to milliseconds(Ba,Ce).Ro...Isomeric I^(π)=8^(-) states have been observed in the even-even N=74 nuclei ^(138)Gd[1],^(136)Sm[2],^(134)Nd[3],^(132)Ce[4],^(130)Ba[5],^(128)Xe[6]with half-lives ranging from nanoseconds(Xe)to milliseconds(Ba,Ce).Rotational bands built on the K^(π)=8^(-) isomer were identified in all these isotones,with the exception of 130Ba.The singleparticle configuration of the isomers have been deduced from theΔI=2 toΔI=1γ-ray intensity branching ratios,which allowed to extract the(gKgR)/Q0 values,and therefore the quasi-particle configuration of the state.展开更多
The complete and incomplete fusion cross sections for ^(6)Li+^(209)Bi were measured using the in-beamγ-ray method around the Coulomb barrier.The cross sections of(deuteron captured)incomplete fusion(ICF)products were...The complete and incomplete fusion cross sections for ^(6)Li+^(209)Bi were measured using the in-beamγ-ray method around the Coulomb barrier.The cross sections of(deuteron captured)incomplete fusion(ICF)products were re-quantified experimentally for this reaction system.The results reveal that the ICF cross section is equivalent to that of complete fusion(CF)above the Coulomb barrier and dominant near or below the Coulomb barrier.A theoretical calculation based on the continuum discretized coupled channel(CDCC)method was performed for the aforementioned CF and ICF cross sections;the result is consistent with the experiments.The universal fusion function(UFF)was also compared with the measured CF cross section for different barrier parameters,demonstrating that the CF suppression factor is significantly influenced by the choice of potential,which can reflect both dynamic and static effects of breakup on the fusion process.展开更多
Excited states of odd-odd nucleus 92Nb and odd-A nucleus 93Nb were populated in the 6 Li+ 89 Y reaction with an incident energy of 34 MeV. The processes that produce 92,93Nb and can be measured by a combination of lig...Excited states of odd-odd nucleus 92Nb and odd-A nucleus 93Nb were populated in the 6 Li+ 89 Y reaction with an incident energy of 34 MeV. The processes that produce 92,93Nb and can be measured by a combination of light charged particle and gamma ray measurements are discussed. Twenty new transitions are observed and eight new levels are constructed in 92Nb, and in addition two new transitions are added to the level scheme of 93Nb. Using shell2 model calculations, the low-lying structure of 9 Nb is investigated and compared with the experimental results.展开更多
文摘The experimental data concerning the58Ni+48Ca reaction at Elab(Ni)=25A MeV,collected by using the CHIMERA 4π device,have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain.As a main criterion for centrality selection we have chosen the flow angle(flow) method,making an event-by-event analysis that considers the shape of events,as it is determined by the eigenvectors of the experimental kinetic-energy tensor.For the selected central events(flow >60°) some global variables,good to characterize the pattern of central collisions have been constructed.The main features of the reaction products were explored by using different constraints on some of the relevant observables,like mass and velocity distributions and their correlations.Much emphasis was devoted,for central collisions,to the competition between fusion-evaporation processes with subsequent identification of a heavy residue and a possible multifragmentation mechanism of a well defined(if any) transient nuclear system.Dynamical evolution of the system and pre-equilibrium emission were taken into account by simulating the reactions in the framework of transport theories.Different approaches have been envisaged(dynamical stochastic BNV calculations + sequential SIMON code,QMD,CoMD,etc.).Preliminary comparison of the experimental data with BNV calculations shows reasonable agreement with the assumption of sequential multifragmentation emission in the mass region of IMFs close to the heavy residues.Possible deviations from sequential processes were found for those IMFs in the region of masses intermediate between the mass of heavy residues and the mass of light IMFs.Further simulations are in progress.The experimental analysis will be enriched also by information obtained inspecting the IMF-IMF correlation function,in order to elucidated the nature of space-time decay property of the emitting source associated with events having the largest IMF multiplicity.
文摘Near degeneracy between two quantum states is usually associated with fundamental symmetries and symmetry breakings in complex many-body systems like atomic nuclei.Pseudospin symmetry was introduced to describe energy degeneracy between single-particle states with quantum numbers(n,l,j=l+1/2)and(n-1,l+2,j=l+3/2)[1-3].
文摘Backbending played a pivotal role in the progress of high-spin structure research[1].This phennomenon was interpreted as a result of band-crossing between two intrinsic configurations which dominate lower-and higher-spin region.Usually the two configurations are differed by two nucleons,which are paired in the former,and unpaired in the latter.According to the strong-coupling scheme,two unpaired quasi-particles can couple to both high-K and low-K configurations in deformed nuclei.Usually only the lower can be identified experimentally since it is favoured by the Gallagher-Moszkowski spin-spin coupling rules[2].
文摘Isomeric I^(π)=8^(-) states have been observed in the even-even N=74 nuclei ^(138)Gd[1],^(136)Sm[2],^(134)Nd[3],^(132)Ce[4],^(130)Ba[5],^(128)Xe[6]with half-lives ranging from nanoseconds(Xe)to milliseconds(Ba,Ce).Rotational bands built on the K^(π)=8^(-) isomer were identified in all these isotones,with the exception of 130Ba.The singleparticle configuration of the isomers have been deduced from theΔI=2 toΔI=1γ-ray intensity branching ratios,which allowed to extract the(gKgR)/Q0 values,and therefore the quasi-particle configuration of the state.
基金Supported by the National Nature Science Foundation of China(U2167204,11975040,1832130)The Brazilian authors thank the partial financial support from CNPq,FAPERJ,and INCT-FNA(Instituto Nacional de Ciência e Tecnologia,Física Nuclear e Aplicações),research Project No.(464898/2014-5)+4 种基金supported by(M.S.)the U.S.Department of Energy,Office of Science,and Office of Nuclear Physics(DE-AC02-06CH11357)supported By the Key Research and Development Program of Guangdong Province,China(2020B040420005)the Basic and Applied Basic Research Foundation of Guangdong Province,China(2021B1515120027)LingChuang Research Project of China National Nuclear Corporation(20221024000072F6-0002-7)the Nuclear Energy Development and Research Project(HNKF202224(28)),and the'111'Center(B20065).
文摘The complete and incomplete fusion cross sections for ^(6)Li+^(209)Bi were measured using the in-beamγ-ray method around the Coulomb barrier.The cross sections of(deuteron captured)incomplete fusion(ICF)products were re-quantified experimentally for this reaction system.The results reveal that the ICF cross section is equivalent to that of complete fusion(CF)above the Coulomb barrier and dominant near or below the Coulomb barrier.A theoretical calculation based on the continuum discretized coupled channel(CDCC)method was performed for the aforementioned CF and ICF cross sections;the result is consistent with the experiments.The universal fusion function(UFF)was also compared with the measured CF cross section for different barrier parameters,demonstrating that the CF suppression factor is significantly influenced by the choice of potential,which can reflect both dynamic and static effects of breakup on the fusion process.
基金Supported by National Natural Science Foundation of China(U1867210,11775098,11475013,U1832130 and 11775316)
文摘Excited states of odd-odd nucleus 92Nb and odd-A nucleus 93Nb were populated in the 6 Li+ 89 Y reaction with an incident energy of 34 MeV. The processes that produce 92,93Nb and can be measured by a combination of light charged particle and gamma ray measurements are discussed. Twenty new transitions are observed and eight new levels are constructed in 92Nb, and in addition two new transitions are added to the level scheme of 93Nb. Using shell2 model calculations, the low-lying structure of 9 Nb is investigated and compared with the experimental results.
