Evidence for Tetrahedral Structure of Calcium-40

Tetrahedral $4α$ and $^{12}\textrm{C}+α$ cluster structures in $^{16}$O

We have investigated structures of the ground and excited states of $^{16}\textrm{O}$ with the method of variation after spin-parity projection in the antisymmetrized molecular dynamics model combined with the generator coordinate method of $^{12}\textrm{C}+α$ cluster. The calculation reasonably reproduces the experimental energy spectra, $E2$, $E3$, $E4$, $IS1$ transitions, and $α$-decay properties. The formation of 4 $α$ clusters has been confirmed from nucleon degrees of freedom in the AMD model without assuming existence of any clusters. They form "tetrahedral" $4α$- and $^{12}\textrm{C}+α…

First order Coriolis-coupling for rotational spectrum of a tetrahedrally-deformed core plus one-particle system

The possible existence of shape-coexisting nuclear configurations with tetrahedral symmetry is receiving an increasing attention due to unprecedented nuclear structure properties, in particular in terms of the exotic 4-fold nucleonic level degeneracies and the expected long lifetimes which may become a new decisive argument in the exotic nuclei research programs. The present article addresses the rotational structure properties of the tetrahedrally-symmetric even-even core configurations coupled with a single valence nucleon. We focus on the properties of the associated Coriolis-coupling Hamil…

丰中子钙同位素壳层结构的演化

Evolution of shell structure in neutron-rich calcium isotopes

我们采用手征有效场论中的相互作用，用耦合团簇方法计算了钙同位素的结合能和低激发态。三核子力的影响被唯象地包括在介质中的两核子相互作用，并考虑到使用Berggren基的粒子连续的耦合。计算得到的42，48，50，52 Ca的基态能量和低2+态能量与实验数据吻合较好，并预测了54 Ca的第一个2+态的激发能为1.9 MeV，只显示出弱的亚壳层闭合.在奇质量核53，55，61Ca中，我们发现正宇称态强烈偏离朴素壳模型。

原子核四面体对称性：可能存在于元素周期表中

Nuclear Tetrahedral Symmetry: Possibly Present Throughout the Periodic Table

在原子核中基本的球壳结构被确定后的半个多世纪里，理论预测表明，可能存在与球形结构相当甚至更强的壳隙。由实际平均场计算支持的群论分析表明，相应的原子核具有$T_d^D$（“双四面体”）对称群的特征，无论是精确的还是近似的。相应的强壳隙结构由于群的4维不可约表示的存在而显著增强，因此它可以被看作是不依赖于平均场的特定实现的几何效应。讨论了在实验中发现相应对称性的可能性。

用量子数投影方法研究核四面体态和高自旋态

Nuclear tetrahedral states and high-spin states studied using quantum number projection method

我们最近发展了一种有效的方法，从最一般的平均场（HFB型）波函数，包括角动量，宇称以及质子和中子粒子数进行全量子数投影。用这种方法，我们已经研究了几种原子核结构机制。在这份报告中，我们讨论了所获得的量子转动光谱的四面体核的国家制定某些实验验证的标准，高自旋状态，集中在摆动和手征带，滴线核作为说明性的例子。

Tetrahedral shape and surface density wave of $^{16}$O caused by $α$-cluster correlations

$α$-cluster correlations in the $0^+_1$ and $3^-_1$ states of $^{12}$C and $^{16}$O are studied using the method of antisymmetrized molecular dynamics, with which nuclear structures are described from nucleon degrees of freedom without assuming existence of clusters. The intrinsic states of $^{12}$C and $^{16}$O have triangle and tetrahedral shapes, respectively, because of the $α$-cluster correlations. These shapes can be understood as spontaneous symmetry breaking of rotational invariance, and the resultant surface density oscillation is associated with density wave (DW) caused by the instab…