标题： 中子共振间距中交叉壳贡献的不可或缺性 显示英文标题

标题： Indispensability of cross-shell contributions in neutron resonance spacing

摘要： 自旋和宇称相关的核能级密度（NLD）通过数值高效的谱分布方法，在配置相互作用壳层模型中获得。计算了$^{24}$Na 和$^{25,26,27}$Mg 核，使用包含从$sd$到$pf$-shell 跨壳激发的完整$sd$-$pf$模型空间。所得到的核能级密度随后用于确定 s 波中子共振间距 (D$_0$)，这是天体物理反应率预测的关键输入之一。 尽管所研究的核子并非富中子核，但来自交叉壳层激发到$pf$壳层的贡献对于解释D$_0$的实验数据是不可或缺的，否则这些数据会被显著高估。 显示英文摘要

摘要： Spin and parity dependent nuclear level densities (NLDs) are obtained for configuration interaction shell model using a numerically efficient spectral distribution method. The calculations are performed for $^{24}$Na, $^{25,26,27}$Mg nuclei using full $sd$-$pf$ model space that incorporates the cross-shell excitations from $sd$ to $pf$-shell. The NLDs so obtained are then employed to determine the s-wave neutron resonance spacing (D$_0$) which is one of the crucial inputs for the predictions of astrophysical reaction rates. Though the considered nuclei are not neutron-rich, the contributions from cross-shell excitations to $pf$-shell are indispensable to explain the experimental data for D$_0$ which otherwise are significantly overestimated.