Abstract Evaporated α-spectra have been measured in coincidence with low energy discrete γ-rays from residual nucleus 68Zn populated by αn evaporation from compound nucleus 73Ge produced in the reaction 64Ni(9Be,αn)68Zn at E ( 9 Be) = 30 MeV. Low energy γ-gated α-particle spectra, for the first time, have been used to extract the nuclear level density (NLD) for the intermediate 69Zn nucleus in the excitation energy range of E ≈ 4-20 MeV. The slope of present NLD data as a function of excitation energy for 69Zn matches nicely with the slope determined from RIPL estimates for NLD at low energies and the NLD from neutron resonance data at neutron separation energy S n . The extracted inverse NLD parameter (k = A/ a ˜ ) has been used to determine the nuclear level density parameter value a at neutron separation energy S n for 69Zn. The cross section of 68Zn(n,γ) capture reaction as a function of neutron energy is then estimated employing the derived a ( S n ) in the reaction code TALYS. It is found that the estimated neutron capture cross section agrees well with the available experimental data without any normalization. The present result indicates that experimentally derived nuclear level density parameter can constrain the statistical model description of astrophysical capture cross section and optimize the uncertainties associated with astrophysical reaction rate.

中文翻译：

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伽马门控粒子谱中 69Zn 的核能级密度及其对 68Zn(n, γ)69Zn 捕获截面的影响

摘要 蒸发的 α 光谱与来自残余核 68Zn 的低能量离散 γ 射线同时被测量，该射线由 64Ni(9Be,αn)68Zn 在 E ( 9 Be) = 30 MeV 反应产生的复合核 73Ge 的 αn 蒸发填充。低能 γ 门控 α 粒子光谱首次用于提取激发能范围为 E ≈ 4-20 MeV 的中间 69Zn 原子核的核能级密度 (NLD)。作为 69Zn 激发能量的函数的当前 NLD 数据的斜率与根据低能量 NLD 的 RIPL 估计值和根据中子分离能量 S n 的中子共振数据确定的 NLD 的斜率很好地匹配。提取的逆 NLD 参数 (k = A/ a ~ ) 已用于确定 69 Zn 在中子分离能 S n 下的核能级密度参数值 a。68Zn(n,γ) 俘获反应的横截面是中子能量的函数，然后使用反应代码 TALYS 中导出的 a ( S n ) 进行估计。发现估计的中子俘获截面与可用的实验数据非常吻合，无需任何归一化。目前的结果表明，实验导出的核能级密度参数可以约束天体物理捕获截面的统计模型描述，并优化与天体物理反应速率相关的不确定性。