摘要
近十年来,从原子核壳模型理论框架出发对重核区原子核集体转动的研究已成为核结构领域的前沿课题.尽管现代计算技术不断拓展大规模壳模型的应用范围,但在处理重核区转动原子核时,壳模型组态空间维数仍远超人类现有的计算能力.核子配对截断作为一种有效的组态空间截断方案,在壳模型研究中得到了广泛应用.以往发展的多种壳模型配对理论成功描述了近球形和过渡区原子核的低激发态性质,然而在转动核问题上面临挑战.本文概述了近年来发展的两种壳模型配对理论框架,分析了SU(3)转动极限情况下多核子系统的核子配对机制,探讨了壳模型配对理论对原子核形状共存、形状演化以及转动带回弯现象的理论解释.这些新方法为壳模型在重核区转动核研究提供了新的机遇和物理图像,有助于人们更深入地理解原子核的复杂结构和行为.
Abstract
Over the past decade,the collective rotation of atomic nuclei in the heavy mass region has emerged as an important area of interest within nuclear structure studies,particularly within the theoretical framework of the nuclear shell model.This field of research has profound implications for understanding the intricate dynamics and interactions within atomic nuclei.Despite the remarkable advances in modern computing techniques that have expanded the applicability of large-scale shell model calculations,the configuration space required to accurately study rotational nuclei in the heavy mass region remains prohibitively large,surpassing the current computational capabilities.This limitation is a critical obstacle to further progress in the field,emphasizing the need for innovative computational and theoretical strategies.To address this challenge,nucleon pair truncation has been introduced as an effective strategy for truncating the configuration space within the shell model.This truncation scheme has been successfully employed in numerous studies,accurately describing the properties of low-lying states in nearly spherical and transitional nuclei.However,the application of pair truncation methods to rotational nuclei presents significant difficulties,necessitating the development of novel theoretical frameworks.The focus of this review is on two such frameworks recently developed within the shell model.The first framework involves the nucleon pair approximation,which utilizes nucleon pairs of specific angular momentum as the fundamental building blocks.This approach significantly reduces the configuration space while retaining the essential physics of collective rotation.The second framework revolves around the projection of intrinsic nucleon pair states,a process that involves constructing"intrinsic"states within the shell model space and subsequently projecting them onto states of good angular momentum.These innovative frameworks open up new avenues for research,providing a more comprehensive understanding of the nucleon pairing mechanism in multi-nucleon systems,particularly in the SU(3)rotational limit.This review further examines the theoretical explanations provided by these pairing theories for several key phenomena observed in rotational nuclei,including the role of nuclear pairing and configuration mixing between different intrinsic states in nuclear shape evolution,the shape coexistence,as well as the backbending phenomenon in rotational bands.The novel methods presented in this review offer exciting new opportunities for studying rotational nuclei in the heavy mass region within the shell model.These methods not only provide valuable insights into the complex structure and behavior of atomic nuclei but also contribute to the ongoing efforts to unify the shell model and collective models within a common theoretical framework.The potential of these methods extends beyond the current research,offering a promising path towards a more comprehensive understanding of nuclear structures,such as nuclear shape-phase transition,subshell effects,octupole deformations,nuclear properties of neutron-rich nuclei and nuclei near the drip lines,resonance state physics,and predictions for superheavy nuclei.
维普
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