Low-energy dipole (LED) excitations in ${}^{20}\mathrm{O}$ were investigated by variation after $K$ projection of $\mathrm{deformation}(\beta$)-constraint antisymmetrized molecular dynamics combined with the generator coordinate method. A low-energy $E1$ mode, which is caused by surface neutron oscillation along the prolate deformation was obtained as the $1_2^{-}$ state. Moreover, a toroidal dipole (TD) mode with vortical nuclear current was obtained as the $1_1^{-}$ state with one-proton excitation on the relatively weak deformation. The low-energy $E1$ mode is a LED excitation peculiar to neutron-rich systems that does not appear in stable oxygen isotopes, whereas the TD (vortical) mode is a LED excitation that was obtained also in ${}^{16}\mathrm{O}$ and ${}^{18}\mathrm{O}$. The TD and $E1$ modes separately appear as the $K^{\pi }=1^{-}$ and $K^{\pi }=0^{-}$ components of the deformed states, respectively, but couple with each other because of $K$ mixing, and shape fluctuation. As a result of the mixing, TD and $E1$ transition strengths are fragmented into the $1_1^{-}$ and $1_2^{-}$ states. The excited bands of $K^{\pi }=0^{+}, K^{\pi }=0^{-}$, and $K^{\pi }=1^{-}$ with cluster structures were also obtained in the energy region higher than the LED states.

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具有反对称分子动力学的 O20 中的低能偶极激发

低能偶极子 (LED) 激发 ${}^{20}\mathrm{哦}$ 经过变异调查 $钾$ 的投影 $\mathrm{形变}(\beta$)-约束反对称分子动力学结合发生器坐标法。一个低能$乙1$ 模式，这是由沿长边形变的表面中子振荡引起的 $1_2^{-}$状态。此外，获得了具有涡旋核电流的环形偶极子 (TD) 模式作为$1_1^{-}$在相对较弱的变形上用单质子激发的状态。低能$乙1$ 模式是富中子系统特有的 LED 激发，不会出现在稳定的氧同位素中，而 TD（涡流）模式是 LED 激发，也是在 ${}^{16}\mathrm{哦}$ 和 ${}^{18}\mathrm{哦}$. TD 和$乙1$ 模式分别显示为 ${钾}^{\pi }=1^{-}$ 和 ${钾}^{\pi }=0^{-}$ 分别是变形状态的分量，但由于 $钾$混合和形状波动。作为混合的结果，TD 和$乙1$ 过渡强度被细分为 $1_1^{-}$ 和 $1_2^{-}$状态。兴奋的乐队${钾}^{\pi }=0^{+}, {钾}^{\pi }=0^{-}$， 和 ${钾}^{\pi }=1^{-}$ 在高于 LED 状态的能量区域中也获得了具有簇结构的结构。