论文标题
将反转岛的南岸扩展到$^{28} $ f
Extending the Southern Shore of the Island of Inversion to $^{28}$F
论文作者
论文摘要
从$^{29} $ ne/$ ne/$ ne/$^{29} $ f梁左右的proton/neutron去除后,首次执行了中子核核$^{28} $ f的详细光谱。 $^{27} $ f $^{(*)}+n $和$^{26} $ f $^{(*)+2n $ cocisciscences均重建了不变的质量光谱。在这两种反应中都观察到了一个接近阈值的状态,并被确定为$^{28} $ f地面状态,具有$ s_n(^{28} $ f $)= - 199(6)$ keV,而对$ 2N $ decay渠道的分析允许$ s_n(^{27} $ f $ f $ f $ f $ f $ f $ f $ s_n = 1620(60)$ kev ded ded允许$ 2N $ decay频道。与壳模型预测和Eikonal模型反应计算的比较允许对某些$^{28} $ f的某些下层水平提出旋转式分配。重要的是,在基态的情况下,重建的$^{27} $ f $+n $动量分布从$^{29} $ f中删除后,表明它主要来自$ 1p_ {3/2} $中子入侵者的配置。这表明$ n = 20 $的反转岛包括$^{28} $ f,很可能$^{29} $ f,并暗示$^{28} $ o不是双重魔术。
Detailed spectroscopy of the neutron-unbound nucleus $^{28}$F has been performed for the first time following proton/neutron removal from $^{29}$Ne/$^{29}$F beams at energies around 230 MeV/nucleon. The invariant-mass spectra were reconstructed for both the $^{27}$F$^{(*)}+n$ and $^{26}$F$^{(*)}+2n$ coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the $^{28}$F ground state, with $S_n(^{28}$F$)=-199(6)$ keV, while analysis of the $2n$ decay channel allowed a considerably improved $S_n(^{27}$F$)=1620(60)$ keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of $^{28}$F. Importantly, in the case of the ground state, the reconstructed $^{27}$F$+n$ momentum distribution following neutron removal from $^{29}$F indicates that it arises mainly from the $1p_{3/2}$ neutron intruder configuration. This demonstrates that the island of inversion around $N=20$ includes $^{28}$F, and most probably $^{29}$F, and suggests that $^{28}$O is not doubly magic.