Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majora...Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction. Under certain conditions, they become the yrast state or yrare state. These states are difficult to decay and become very stable. This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.展开更多
Thorium-229 possesses the lowest first nuclear excited state,with an energy of approximately 8 eV.The extremely narrow linewidth of the first nuclear excited state,with an uncertainty of 53 THz,prevents direct laser e...Thorium-229 possesses the lowest first nuclear excited state,with an energy of approximately 8 eV.The extremely narrow linewidth of the first nuclear excited state,with an uncertainty of 53 THz,prevents direct laser excitation and realization of the nuclear clock.We present a proposal using the Coulomb crystal of a linear chain formed by229Th^(3+)ions,where the nuclei of229Th3+ions in the ion trap are excited by the electronic bridge(EB)process.The 7 P1∕2state of the thorium-229 nuclear ground state is chosen for EB excitation.Using the two-level optical Bloch equation under experimental conditions,we calculate that 2 out of 36 prepared thorium ions in the Coulomb crystal can be excited to the first nuclear excited state,and it takes approximately 2 h to scan over an uncertainty of 0.22 eV.Taking advantage of the transition enhancement of EB and the long stability of the Coulomb crystal,the energy uncertainty of the first excited state can be limited to the order of 1 GHz.展开更多
An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly(α-methylstyrene)(PαMS) chains is studied, in which the effect of large side group...An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly(α-methylstyrene)(PαMS) chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.展开更多
When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder...When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder are investigated by using rotational isomeric state model. Using the average conformational energy and entropy and the average length, we can determine the elastic force f, or the fraction of the energy term to the total force f(e)/f where f(e) = partial derivative /partial derivative < r > and f = partial derivative /partial derivative < r >. Comparisons with experimental data are also made. The results of these microscopic calculations are discussed in terms of the macroscopic phenomena of rubber elasticity.展开更多
We investigate the properties of the Ce isotopes with neutron number N =60 - 90 and the properties of the heavy nuclei near 242Am within the framework of deformed relativistic mean-field (RMF) theory. A systematic c...We investigate the properties of the Ce isotopes with neutron number N =60 - 90 and the properties of the heavy nuclei near 242Am within the framework of deformed relativistic mean-field (RMF) theory. A systematic comparison between theoretical results and experimental data is made. The calculated binding energies, two-neutron separation energies, and two-proton separation energies are in good agreement with experimental ones. The variation trend of experimental quadrupole deformation parameters on the Ce isotopes can be approximately reproduced by the RMF model. It is found that there exists an abnormally large deformation in the ground state of proton-rich Ce isotopes. This phenomenon can be the general behavior of proton-rich nuclei on the neighboring isotopic chains such as Nd and Sin isotopes. For the heavy nuclei near ^242 Am the properties of the ground state and superdeformed isomeric state can be approximately reproduced by the RMF model. The mechanism of the appearance of anomalously large deformation or superdeformation is analyzed and its influence on nuclear properties is discussed. Parther experiments to study the anomalously large deformation in some proton-rich nuclei are suggested.展开更多
Low-lying states in odd-Z odd-mass nuclei at the proton drip-line beyond lead have recently been studied through fusion-evaporation reactions using a gas-filled recoil separator. Isomeric 1/2+and13/2+states have been ...Low-lying states in odd-Z odd-mass nuclei at the proton drip-line beyond lead have recently been studied through fusion-evaporation reactions using a gas-filled recoil separator. Isomeric 1/2+and13/2+states have been observed in odd-mass astatine and francium nuclei. The systematic behaviour of the level energies of these states have been studied and a similarity between the 1/2+state in astatine and francium has been found. Furthermore, the 13/2+state has been observed in the francium nuclei with an oblate behaviour suggesting a coupling of the i13/2proton to the 2p- 2h intruder excitation.展开更多
A systematic study on the a-decay half-lives of nuclei in the range 93≤Z≤118 is performed by employing various versions of proximity potentials.To obtain more reliable results,deformation terms are included up to he...A systematic study on the a-decay half-lives of nuclei in the range 93≤Z≤118 is performed by employing various versions of proximity potentials.To obtain more reliable results,deformation terms are included up to hexadecapole(β_(4))in the spherical-deformed nuclear and Coulomb interaction potentials.First,the favored a-de-cay processes in this region are categorized as even-even,odd A,and odd-odd nuclei.Second,they are grouped into two transitions:ground state to ground state and ground state to isomeric states.Owing to the comparison of their root-mean-square deviations(RMSD's),Bassll and Ngo80 have the lowest values and better reproduce experimental data.Moreover,by considering preformation probability within the cluster formation model,the results validate the significant reduction in root-mean-square deviations obtained for different versions of proximity.Hence,the deviation between the calculated and experimental data is detracted.展开更多
The neutron rich nucleus 193Os was produced in the 192Os(TLi, 6Li)193Os reaction. An isomeric state based on the 9/2-[505] Nilsson orbital was identified in the present work. The half-life of the isomeric state was ...The neutron rich nucleus 193Os was produced in the 192Os(TLi, 6Li)193Os reaction. An isomeric state based on the 9/2-[505] Nilsson orbital was identified in the present work. The half-life of the isomeric state was extracted and discussed in terms of the K quantum number. A level scheme built on the isomeric state was proposed based on the experimental data.展开更多
Deformed odd-mass nuclei are ideal examples where the interplay between single-particle and collective degrees of freedom can be studied. Inspired by the recent experimental high-spin data in the odd-proton nuclide 17...Deformed odd-mass nuclei are ideal examples where the interplay between single-particle and collective degrees of freedom can be studied. Inspired by the recent experimental high-spin data in the odd-proton nuclide 171 Tm, we perform projected shell model(PSM) calculations to investigate structure of the ground band and other bands based on isomeric states. In addi- tion to the usual quadrupole-quadrupole force in the Hamiltonian, we employ the hexadecapole-hexadecapole(HH) interac- tion, in a self-consistent way with the hexadecapole deformation of the deformed basis. It is found that the known experi- mental data can be well described by the PSM calculation. The effect of the HH force on the quasiparticle isomeric states is discussed.展开更多
文摘Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction. Under certain conditions, they become the yrast state or yrare state. These states are difficult to decay and become very stable. This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.
基金the National Natural Science Foundation of China(No.11804372).
文摘Thorium-229 possesses the lowest first nuclear excited state,with an energy of approximately 8 eV.The extremely narrow linewidth of the first nuclear excited state,with an uncertainty of 53 THz,prevents direct laser excitation and realization of the nuclear clock.We present a proposal using the Coulomb crystal of a linear chain formed by229Th^(3+)ions,where the nuclei of229Th3+ions in the ion trap are excited by the electronic bridge(EB)process.The 7 P1∕2state of the thorium-229 nuclear ground state is chosen for EB excitation.Using the two-level optical Bloch equation under experimental conditions,we calculate that 2 out of 36 prepared thorium ions in the Coulomb crystal can be excited to the first nuclear excited state,and it takes approximately 2 h to scan over an uncertainty of 0.22 eV.Taking advantage of the transition enhancement of EB and the long stability of the Coulomb crystal,the energy uncertainty of the first excited state can be limited to the order of 1 GHz.
文摘An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly(α-methylstyrene)(PαMS) chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.
基金This research was financially supported by the National Natural Science Foundation of China and the National Basic Research Project "Macromolecular Condensed State" from STCC
文摘When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder are investigated by using rotational isomeric state model. Using the average conformational energy and entropy and the average length, we can determine the elastic force f, or the fraction of the energy term to the total force f(e)/f where f(e) = partial derivative /partial derivative < r > and f = partial derivative /partial derivative < r >. Comparisons with experimental data are also made. The results of these microscopic calculations are discussed in terms of the macroscopic phenomena of rubber elasticity.
基金国家自然科学基金,国家重点基础研究发展计划(973计划),中国科学院知识创新工程项目,the Research Fund for the Doctoral Program of Higher Education of China
文摘We investigate the properties of the Ce isotopes with neutron number N =60 - 90 and the properties of the heavy nuclei near 242Am within the framework of deformed relativistic mean-field (RMF) theory. A systematic comparison between theoretical results and experimental data is made. The calculated binding energies, two-neutron separation energies, and two-proton separation energies are in good agreement with experimental ones. The variation trend of experimental quadrupole deformation parameters on the Ce isotopes can be approximately reproduced by the RMF model. It is found that there exists an abnormally large deformation in the ground state of proton-rich Ce isotopes. This phenomenon can be the general behavior of proton-rich nuclei on the neighboring isotopic chains such as Nd and Sin isotopes. For the heavy nuclei near ^242 Am the properties of the ground state and superdeformed isomeric state can be approximately reproduced by the RMF model. The mechanism of the appearance of anomalously large deformation or superdeformation is analyzed and its influence on nuclear properties is discussed. Parther experiments to study the anomalously large deformation in some proton-rich nuclei are suggested.
基金Academy of Finland under the Finnish Center of Excellence Programmes(2006-2011,2012-2017)EURONS(European Comissiom)(RII3-CT-2004-506065)EU 7th Framework Programme(262010)(ENSAR)
文摘Low-lying states in odd-Z odd-mass nuclei at the proton drip-line beyond lead have recently been studied through fusion-evaporation reactions using a gas-filled recoil separator. Isomeric 1/2+and13/2+states have been observed in odd-mass astatine and francium nuclei. The systematic behaviour of the level energies of these states have been studied and a similarity between the 1/2+state in astatine and francium has been found. Furthermore, the 13/2+state has been observed in the francium nuclei with an oblate behaviour suggesting a coupling of the i13/2proton to the 2p- 2h intruder excitation.
文摘A systematic study on the a-decay half-lives of nuclei in the range 93≤Z≤118 is performed by employing various versions of proximity potentials.To obtain more reliable results,deformation terms are included up to hexadecapole(β_(4))in the spherical-deformed nuclear and Coulomb interaction potentials.First,the favored a-de-cay processes in this region are categorized as even-even,odd A,and odd-odd nuclei.Second,they are grouped into two transitions:ground state to ground state and ground state to isomeric states.Owing to the comparison of their root-mean-square deviations(RMSD's),Bassll and Ngo80 have the lowest values and better reproduce experimental data.Moreover,by considering preformation probability within the cluster formation model,the results validate the significant reduction in root-mean-square deviations obtained for different versions of proximity.Hence,the deviation between the calculated and experimental data is detracted.
基金Supported by National Natural Science Foundation of China(10905075)
文摘The neutron rich nucleus 193Os was produced in the 192Os(TLi, 6Li)193Os reaction. An isomeric state based on the 9/2-[505] Nilsson orbital was identified in the present work. The half-life of the isomeric state was extracted and discussed in terms of the K quantum number. A level scheme built on the isomeric state was proposed based on the experimental data.
基金supported by the National Natural Science Foundation of China(Grant Nos.11305059,11275067,11135005 and 11275068)the National Basic Research Program of China(Grant No.2013CB834401)the C3S2 Computing Center of School of Science for their calculation support
文摘Deformed odd-mass nuclei are ideal examples where the interplay between single-particle and collective degrees of freedom can be studied. Inspired by the recent experimental high-spin data in the odd-proton nuclide 171 Tm, we perform projected shell model(PSM) calculations to investigate structure of the ground band and other bands based on isomeric states. In addi- tion to the usual quadrupole-quadrupole force in the Hamiltonian, we employ the hexadecapole-hexadecapole(HH) interac- tion, in a self-consistent way with the hexadecapole deformation of the deformed basis. It is found that the known experi- mental data can be well described by the PSM calculation. The effect of the HH force on the quasiparticle isomeric states is discussed.