$^{204}$ At的高自旋态：同质异能态和剪切能带结构
High spin states of $^{204}$At: isomeric states and shears band structure
摘要：
通过$^{12}$ C + $^{197}$ Au聚变蒸发反应，将贫中子反式铅核$^{204}$ At的高自旋态布居到$\sim 8\,{\rm MeV}$激发态.通过即时和延迟$γ$ -射线发射的相关水平的衰变进行了研究，以评估潜在的核结构。水平方案，这是部分已知的，进一步扩大。从我们的测量中建立了具有观察到的寿命$τ=52 \pm 5\, {\rm ns}$的异构体$16^+$能级。试图解释激发态的基础上多准粒子和空穴结构，涉及$2f_{5/2}$，$1h_{9/2}$，和$1i_{13/2}$壳模型状态，以及适度的核心激发。在自旋宇称范围内的磁偶极子能带结构：~ $16^+ - 23^+$得到了确认，并进行了更详细的评估，包括丢失的交叉$E2$跃迁。沿剪切带的带交叉进行了观察和比较，在邻近的中子缺乏$^{202}$ Bi，$^{205}$ Rn同位素和$^{203}$在同位素的类似现象的证据。基于沿能带跃迁的测量$B(M1)/B(E2)$值与基于半经典模型的估计值的比较，建立了$^{204}$ At的剪切带以及能级方案。
英文摘要：
High-spin states of neutron deficient Trans-Lead nucleus $^{204}$At were populated up to $\sim 8\,{\rm MeV}$ excitation through the $^{12}$C + $^{197}$Au fusion evaporation reaction. Decay of the associated levels through prompt and delayed $γ$-ray emissions were studied to evaluate the underlying nuclear structure. The level scheme, which was partly known, was extended further. An isomeric $16^+$ level with observed lifetime $τ=52 \pm 5\, {\rm ns}$, was established from our measurements. Attempts were made to interpret the excited states based on multi quasiparticle and hole structures involving $2f_{5/2}$, $1h_{9/2}$, and $1i_{13/2}$ shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~$16^+ - 23^+$ was confirmed and evaluated in more detail, including the missing cross-over $E2$ transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighbouring neutron deficient $^{202}$Bi, $^{205}$Rn isotones and the $^{203}$At isotope. Based on comparison of the measured $B(M1)/B(E2)$ values for transitions along the band with the semiclassical model based estimates, the shears band of $^{204}$At was established along with the level scheme.
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