Nuclear contact is a key quantity to describe the nucleon-nucleon short-range correlations (SRCs). While they have been determined by electron scattering experiments for selected stable nuclei, nuclear contacts are largely unknown for unstable nuclei. In this work, we study nuclear contacts for a number of nuclei in the vicinity of the doubly magic 132Sn from the theoretical perspective, with special emphasis on unstable nuclei. We find that the proton-proton contact generally gets suppressed by the excess neutrons for the Sn isotopes, resembling the suppression of α-cluster formation reported recently for the same isotopic chain (J. Tanaka et al., 2021 [46]). This might suggest a hidden universal aspect of SRCs and α clustering, two different kinds of nuclear correlations. Moreover, we reveal a model-independent correlation between the proton-proton contact and the root-mean-square radius of proton density distributions for Sn isotopes. Meanwhile, a linear relation is found between the proton-proton contact and the proton number for the N=82 isotones. Our results can be helpful for future experimental studies of SRCs in unstable nuclei at advanced facilities worldwide.

中文翻译：

---

不稳定核的核接触


核接触是描述核子-核子短程相关性（SRC）的关键量。虽然它们是通过电子散射实验对选定的稳定核进行确定的，但对于不稳定核来说，核接触在很大程度上是未知的。在这项工作中，我们从理论角度研究了双魔132Sn附近的多个原子核的核接触，特别关注不稳定的原子核。我们发现质子-质子接触通常会受到 Sn 同位素过量中子的抑制，类似于最近报道的同一同位素链 α 簇形成的抑制（J. Tanaka 等人，2021 [46]）。这可能表明 SRC 和 α 聚类（两种不同类型的核相关性）隐藏的普遍性。此外，我们揭示了锡同位素质子-质子接触与质子密度分布的均方根半径之间的模型无关的相关性。同时，对于N=82等位素，质子-质子接触与质子数之间存在线性关系。我们的结果有助于未来在全球先进设施中对不稳定核中的 SRC 进行实验研究。