$γ$的观测--建立在156 Dy非基态组态上的振动和排列
Observation of $γ$-vibrations and alignments built on non-ground-state configurations in 156Dy
摘要：
在所有变形核中最低的$K^π=2_γ^+$转动带的确切性质仍然不清楚。传统上，它们被假定为原子核形状在垂直于原子核对称轴的$γ$自由度上的集体振动。在高j核子通常的后弯转动排列之后，很少有这样的$γ$带被追踪到。我们利用65 MeV的148 Nd（12 C，4 n）156 Dy反应，用γ射线阵列观测了N=90核156 Dy的正宇称带结构。观察到$K^π=2_γ^+$ $γ$ -带的偶自旋和奇自旋成员分别为32+和31+。这个旋转带忠实地跟踪最高自旋的基态构型。观察到建立在对齐的yraast S带上的可能的$γ$振动的成员自旋为28+和27+。一个偶数自旋正宇称带，观察到自旋24+，是一个对齐的S带的候选人建立在高级零配置的$0_2^+$状态在676千电子伏。该带与$0_2^+$带的交叉点在$\hbarω$ = 0.28（1）MeV处，并且与不产生任何对电子对的阻断的$0_2^+$带的构型一致。
英文摘要：
The exact nature of the lowest $K^π=2_γ^+$ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the $γ$ degree of freedom perpendicular to the nuclear symmetry axis. Very few such $γ$-bands have been traced past the usual back-bending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus 156Dy, using the 148Nd(12C,4n)156Dy reaction at 65 MeV, observing the resulting $γ$-ray transitions with the Gammasphere array. The even- and odd-spin members of the $K^π=2_γ^+$ $γ$-band are observed to 32+ and 31+ respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible $γ$-vibration built on the aligned yrast S-band are observed to spins 28+ and 27+. An even-spin positive-parity band, observed to spin 24+, is a candidate for an aligned S-band built on the seniority-zero configuration of the $0_2^+$ state at 676 keV. The crossing of this band with the $0_2^+$ band is at $\hbarω$= 0.28(1) MeV and is consistent with the configuration of the $0_2^+$ band not producing any blocking of the monopole pairing.
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