Recent progress in the structure and dynamics of nuclear linear-chain α clusters within the framework of covariant density functional theory is reviewed.The covariant density functional theory does not a priori assume the existence of α clusters and provides a microscopic and self-consistent description of the corresponding linear-chain cluster structure.By combin-ing the covariant density functional theory with the cranking model,the coherent effects of nuclear spin and isospin on the linear-chain cluster structure of carbon isotopes are revealed.Owing to the effects of the Coriolis term in the cranking covariant density functional theory,σ orbitals show a reduction in energy with the rotational frequency and are occupied by valence neutrons,indicating that the linear-chain cluster structures are more feasible in fast-rotating neutron-rich nu-clei.A similar mechanism exists for the 3a and 4α linear-chain cluster structures in proton-rich nuclei,wherein protons occupy σ orbitals at lower angular momenta than those observed for neutrons.Based on the calculations of the covari-ant density functional theory in a three-dimensional lattice space,the linear-chain cluster configuration in 12C is shown as a state with the minimum energy on the potential energy surface for rotational frequencies of 2.0-3.5 MeV,thereby demonstrating the stability of the linear-chain cluster structure against nuclear bending motion and fission.Furthermore,the development of the time-dependent covariant density functional theory enables the dynamical study of the linear-chain cluster structure.Investigations of the microscopic dynamics of the linear-chain cluster states for 12C and 14C isotopes in the reactions 4He+8Be and 4He+10Be show that the dynamical isospin effects by the valence neutrons impede the longitudinal oscillations of clusters,thereby prolonging the lifetime of the linear-chain cluster states.
关键词
协变密度泛函理论/原子核结团/链式结团结构/原子核转动/共振散射
Key words
covariant density functional theory/nuclear clusters/linear chain cluster structure/nuclear rotation/resonance scattering
万方数据