极端条件下的原子核同核异能态

One of the frontiers of the current nuclear physics research is nuclear structure in extreme conditions. Isomers, among others, play a special role because of their simple configuration and stability associated with their hindered decay. In this project we plan to investigate high-K isomers and shape isomers in superheavy nuclei, extremely neutron-rich nuclei and those with extremely high excitation-energy and spin, using configuration-constrained potential-energy-surface calculations and Total-Routhian-Surface calculations. We will predict more isomers by systematic calculations, study the shape and broken-pair excitation effects on each other, study the coexistence and competition of high-K and shape isomerisms, and explore the neutron emitting of neutron-rich isomers and the existence of isomers beyond the neutron-drip line. Besides the significance in stability of exotic nuclei and astrophysical nucleonsynthesis, the isomers provide sensitive probe to the single-particle states, shell structure, deformation and pairing property in extreme conditions, and serve as “stepping stones” towards other nuclear structures. In addition, long-lived highly-excited isomers have potential application in energy storage. When reproducing the observables, our calculations will also provide useful predictions for future experiments.

极端条件下的原子核结构是当今核物理研究的一个热点，同核异能态因其简单的组态和与长寿命相应的较高稳定性在核结构研究中地位特殊。在本项目中，我们拟应用组态限制势能面计算和总罗斯面计算研究超重核、极端丰中子核和极端高激发能高自旋的高K同核异能态和形状同核异能态，包括系统性的计算给出更多的同核异能态，形变与拆对激发的相互影响，高K和形状同核异能机制的共存与竞争，并探索丰中子同核异能态的中子衰变和中子滴线区的同核异能态等。这些同核异能态除了在奇特核稳定性和天体核合成上的意义，还是极端条件下原子核单粒子能级、壳结构、形状和对相互作用性质的灵敏探针，也可作为跳板通向原子核的其他性质，同时长寿命高激发能的同核异能态还具有应用上的价值,重现实验的同时我们还为将来的实验提供理论预言。

应用含高阶形变的组态限制势能面计算和基于推转壳模型的TRS (Total Routhian Surface)计算，我们研究了极端丰中子核和超重核中的形变同核异能态和高K同核异能态，重点讨论了形变、激发能、衰变模式等因素对极端不稳定核存在和稳定性的影响。极端丰中子核如N=100、102、104，A~160中系统性地存在两准粒子高K同核异能态，而且高阶形变如beta6在这里有重要影响，考虑beta6的理论结果能更好地重现已有的实验数据。特别地，实验在这里观测到了最轻的四准粒子高K同核异能态，我们从高阶形变很好地阐明了它的形成。对于超重核，我们研究了Z=120~140, N=170~200质量区，这里有丰富的形状及其演化现象，普通扁椭球和超形变扁椭球的共存和竞争，导致其中一者可成为形状同核异能态，甚至出现超形变扁椭球基态。更重要的是，这里系统性地存在低激发能的超形变扁椭球高K态，典型的如N=196、198同中子素链中的的K^pi=15-态。它们的超形变扁椭球形状、极低的激发能、很高的K值、拆对效应可以降低gamma跃迁、alpha衰变、裂变的概率，从而对于这里超重核的存在和稳定性有重要意义。另外，我们还在发展Cassinian ovals parametrization的裂变位垒计算模型，将用于后续的研究。