锌-64的统计与非统计γ衰变性质
Statistical and non-statistical $γ$-decay properties of $^{64}$Zn
AI总结：
本研究结合Oslo方法与NewSUBARU装置的实验数据，探究⁶⁴Zn的γ衰变性质，确定其NLD符合类恒温模型，发现基态衰变的非统计效应及γSF的低能增强，为核结构研究提供关键数据。
AI中文摘要：
我们利用Oslo方法对锌-64（⁶⁴Zn）的γ衰变性质开展研究，该方法基于⁶⁴Zn(p,p'γ)数据，结合在NewSUBARU装置测得的⁶⁴Zn(γ,n)截面测量结果。借助Oslo方法，我们测量了中子阈以下的γ射线强度函数（γSF）和核能级密度（NLD）。观测发现，锌-64准连续区的NLD趋势最符合类恒温模型，其温度参数T_CT=1.21(5) MeV。令人惊讶的是，我们发现从准连续区直接跃迁到0⁺基态的γ射线跃迁被强烈抑制，抑制因子κ≈0.5，这可能表明基态衰变中存在非统计效应，例如源于核形状差异。对于中子分离能以上的γ能量，NewSUBARU的(γ,n)数据集探测到了巨偶极共振的显著部分。此外，我们发现Oslo方法测得的γSF表现出相当平滑的行为，在Eγ<4 MeV时存在明显的低能增强（LEE）。
英文摘要：
We present a study on the $γ$-decay properties of $^{64}$Zn using the Oslo method on $^{64}$Zn($p,p^\prime γ$) data combined with $^{64}$Zn$(γ,n)$ cross-section measurements at the NewSUBARU facility. With the Oslo method, we have measured the $γ$-ray strength function ($γ$SF) and the nuclear level density (NLD) below the neutron threshold. We observe that the NLD trend in the quasi-continuum region of $^{64}$Zn is best characterized by a constant-temperature-like model. %with temperature parameter $T_{\rm CT}=1.21(5)$ MeV. Surprisingly, we find that $γ$-ray transitions from the quasi-continuum decaying directly to the $0^+$ ground state seem to be strongly hindered with a hindrance factor of $κ\approx 0.5$, which could be an indication of non-statistical effects in the ground-state decay due to, \textit{e.g.}, differences in nuclear shapes. For $γ$ energies above the neutron separation energy, the NewSUBARU ($γ, n$) data set probes a significant part of the giant dipole resonance. Furthermore, we find that the Oslo-method $γ$SF shows a rather smooth behavior, with a clear low-energy enhancement (LEE) for $E_γ < 4$ MeV.
