Variation after $K$-projection in antisymmetrized molecular dynamics for low-energy dipole excitations in ${}^{10}$Be and ${}^{16}$O

Abstract

For study of dipole excitations, a new method of variation after $K$-projection in the framework of antisymmetrized molecular dynamics (AMD) with the deformation $\beta$ constraint was proposed. The method was applied to ${}^{10}$Be and ${}^{16}$O to describe low-energy dipole excitations and found to be a useful and economical approach for dipole excitations. In the application to ${}^{10}$Be, two dipole states in low-energy region were described. For ${}^{16}$O, the $1_1^{-}$ and $1_2^{-}$ states with remarkable dipole strengths were obtained. The $1_1^{-}$ state is characterized by significant toroidal dipole (TD) and compressional dipole strengths, whereas the $1_2^{-}$ has significant TD strength and shows a developed $\alpha +{}^{16}$O cluster structure. Dipole properties in ${}^{16}$O were discussed by analysis of current densities of the dipole transitions.

Comments: 22 pages, 11 figures