N=100附近同中子偶偶核高-K转动带的组态限制计算

Configuration-constrained calculations of high-K rotational bands in even-even isotones around N=100

通过基于Skyrme Hartree-Fock(HF)的组态限制推转壳模型方法系统计算了N=100附近同中子原子核的基态带和高-K转动带.采用粒子数守恒(particle-number-conserving,PNC)方法处理对相互作用.计算的基带和边带都很好地描述了实验转动惯量.对160Sm,164Dy,166Er和168Yb同中子核的K^π=6^-转动带,168Er和170Yb的K^π=4^-转动带以及170Er和172Yb的K^π=6^-转动带进行了系统的研究,并对其进行了相应的微观解释.同时,还预言了158Nd和162Gd同中子核的K^π=6^-转动带以及160Nd,162Sm,164Gd和166Dy同中子核的K^π=4^-转动带.深入研究了原子核转动特性,并对将来的实验提供了有用的信息.

Nuclear rotational spectroscopy has been extensively investigated in experimental and theoretical studies.In the collective model,a nucleus can be excited in two ways.One is by breaking pairs of nucleons and exciting nucleons to a higher level.An excited state with a higher K-value sometimes has a long lifetime.Usually those states with lifetimes longer than 1 ns are called isomeric state because of forbidden transitions from high K to low K state.The other way is by collective motions,like rotation and vibration.A rotational band built on the multi-particle state is called a sideband.In general,a nucleus can have more than one sideband.Investigations of sidebands can provide rich information about the nucleus structure,like single-particle level,nuclear shape,and electromagnetic transitions and so on.The traditional total Routhian surface method,which is a powerful tool for investigating nuclear rotation,has been successfully used to describe yrast bands.However,it often encounters non-convergence problems when calculating sidebands.To overcome this problem,we recently developed a configuration-constrained cranking Skyrme Hartree-Fock mean-field calculation with pairing treated by the particle-number-conserving(PNC)method for sidebands.The PNC pairing method follows the technique of a"standard"shell model,which diagonalizes the Hamiltonian in a truncated model space and guarantees the conservation of the particle number.The rare-earth(Z=57-71)neutron-rich nuclides are good candidates for investigating the high-K rotational bands.In this mass region,nuclei with N≥90 are known to be well deformed and many high-j orbitals exist near the neutron and proton Fermi surfaces.These orbitals can form various multi-particle configurations and lead to high-K rotational sidebands.We perform configuration-constrained cranking Skyrme Hartree-Fock mean-field calculations with pairing treated using the PNC method for the high-K rotational bands in even-even isotones near N=100.The K^π=6^- rotational bands in160Sm,164Dy,166Er,168Yb,170Er,and172Yb and the K^π=4^- rotational bands in 168Er and 170Yb have been observed during experiments.Kπ=6-isomers were first observed in very neutron-rich nuclei,i.e., 158Nd,164Sm,and 166Gd.Further,K^π=4^- isomers were first observed in neutron-rich N=100 isotones,i.e.,160Nd,162Sm,and 164Gd.Theoretically,several models have been used to study these neutron-rich nuclei,including the cranked shell model,projected shell model,deformed Hartree-Fock method,cranking PNC method,and quasiparticle random phase approximation.We systematically investigated these high-Krotational bands and the ground state bands in N=98,100,and 102 isotones using the configuration-constrained cranking Skyrme Hartree-Fock mean-field calculation with PNC pairing.The Skyrme force of SKM* is adopted.The pairing strength is determined using the odd-even mass difference and a three-point formula,which includes the mean-field and blocking effects.The calculations reproduce the experimental moments of inertia of both the ground state and sidebands well.Configurations are assigned to the observed high-K rotational bands.Further,we predict possible high-K rotational bands in158Nd,162Gd,160Nd,162Sm,164Gd,and 166Dy.This study on high-K rotational bands can provide new insights into the structure of the states,and the predictions may provide useful information for future experiments.