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近库仑位垒重离子熔合反应动力学的系统研究
Systematic study of the heavy-ion fusion dynamics at near-barrier energies

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王兵 1   温凯 2   赵维娟 1   赵恩广 3   周善贵 4 *  
文摘 近库仑位垒重离子俘获与熔合是一个典型的多自由度耦合的位垒穿透过程.理论上,解耦合道方程可以描述多维位垒穿透问题.在本征道的理论框架下,多自由度的耦合会使单个位垒劈裂成一系列的分立位垒.基于位垒分布的思想,发展了一个经验的耦合道模型,系统地研究了220个反应体系的俘获激发函数.在该模型中,相对运动和内禀自由度的耦合效应及中子转移效应一并包含在一个非对称的高斯型位垒分布函数中.基于特定的核-核相互作用势,提出了计算位垒分布函数参数的经验公式.结果表明:本文发展的经验耦合道模型能够系统地描述近库仑位垒能区的俘获截面.该经验耦合道模型不仅能够解释俘获动力学中的重要现象,还有望对合成超重核的反应体系的俘获激发函数提供理论预言.本文将简要地评述描述近库仑位垒重离子俘获反应的相关模型,介绍经验耦合道模型,并基于该模型讨论振动耦合、转动耦合及中子转移效应对俘获截面的影响.
其他语种文摘 In recent decades, the study of capture and fusion dynamics in heavy-ion collisions has been a subject of intense experimental and theoretical interests because the heavy-ion capture not only is of central importance for nucleosynthesis but also can reveal rich interplay between nuclear structure and reaction dynamics. Theoretically, the heavy-ion capture and fusion processes at energies near the Coulomb barrier can be treated as a multidimensional barrier penetration problem. The multidimensional barrier penetration process can be described by solving the coupled-channel equations, i.e., the coupled-channel (CC) model. However, for heavy reaction systems, it is necessary to take into account a large number of channels which is not easy to realize in the CC model. Moreover, the structure information of the interacting nuclei are needed as inputs. Therefore, full CC calculations become intractable in many cases including many fusion reactions leading to superheavy nuclei. On the other hand, in the eigenchannel framework, the couplings to other channels split the single potential barrier into a set of discrete barriers. Based on the concept of the barrier distribution, several empirical CC approaches have been developed. Recently, we have developed an empirical coupled-channel (ECC) model and performed a systematic study of capture excitation functions for 220 reaction systems. In this ECC model, an asymmetric Gaussian-form barrier distribution function was used to take effectively into account the effects of inelastic excitation couplings and neutron transfer coupling. Based on the interaction potential between the projectile and the target, empirical formulas were proposed for the parameters of the barrier distribution according to the static and dynamical deformations of the two colliding nuclei. For the vibrational coupling effect and the rotational coupling effect, the parameters of the empirical formulas were given, respectively. For spherical reaction systems (vibrational coupling effect), the width of the barrier distribution increases with the charge product of the reaction system, while for the deformed reaction systems (rotational coupling effect), besides the charge product of the reaction system, the width of the barrier distribution is also related to the static deformation parameters of the projectile and the target. For some reaction systems, the coupling effects of the positive Q-value neutron transfer (PQNT) channels are needed to explain the enhancement of sub-barrier capture cross sections. In this ECC model, the effects of PQNT are simulated by broadening the barrier distribution. Moreover, the positive Q value for one neutron pair transfer is used to broaden the barrier distribution in the present model. Among these 220 reaction systems, there are 89 systems with positive Q value for one neutron pair transfer channel. The calculated capture cross sections of most of these 89 reaction systems are in good agreement with the experimental values, which implies that the Q value for one neutron pair transfer is very important to understanding of the coupling to PQNT channels. Generally speaking, the ECC model together with the empirical formulas for parameters of the barrier distribution works quite well in the description of the capture cross sections at near-barrier energies. This model can provide useful information on capture dynamics and predictions of capture cross sections for the synthesis of superheavy nuclei. In the present paper, we will review this ECC model and its applications.
来源 科学通报 ,2017,62(22):2480-2491 【核心库】
DOI 10.1360/N972016-01460
关键词 熔合动力学 ; 位垒分布 ; 经验耦合道模型 ; 耦合道效应 ; 中子转移效应
地址

1. 郑州大学物理工程学院, 郑州, 450001  

2. 中国科学院理论物理研究所, 中国科学院理论物理前沿重点实验室, 北京, 100190  

3. 中国科学院理论物理研究所, 中国科学院理论物理前沿重点实验室;;兰州重离子加速器国家实验室, 北京, 100190  

4. 中国科学院理论物理研究所, 中国科学院理论物理前沿重点实验室;;兰州重离子加速器国家实验室;;量子效应及其应用协同创新中心, 北京, 100190

语种 中文
文献类型 研究性论文
ISSN 0023-074X
学科 物理学
基金 国家自然科学基金国家杰出青年科学基金 ;  国家自然科学基金 ;  国家973计划 ;  中国科学院知识创新工程重要方向项目
文献收藏号 CSCD:6087174

参考文献 共 94 共5页

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引证文献 1 篇

1 周善贵 超重原子核与新元素研究 原子核物理评论,2017,34(3):318-331
被引 8 次

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