154Sm+160Gd深度非弹性散射发现新富中子同位素

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本文主要探讨了在高能物理领域的一项重要研究，即使用两种微观动力学方法——改进的量子分子动力学（Improved Quantum Molecular Dynamics, ImQMD）模型和时间依赖的哈特里-福克（Time-Dependent Hartree-Fock, TDHF）理论来研究154Sm与160Gd的深层非弹性散射。这项工作发表于《物理快报B》760期，236-241页，是开放存取的文章。研究集中在Bass势垒以上的能量下，这两个重核之间的反应，特别关注的是新富中子同位素的生成。实验结果显示，尽管在440 MeV的入射能量下，由于强烈的库仑排斥作用，原本可能存在的融合过程并未发生，导致捕获腔消失。碰撞中形成的双核系统接触时间短暂，大约只有700 femtometer/cubic centimeter (fm/c)。利用ImQMD-v2.2模型，结合描述碎片二次衰变的统计代码GEMINI，研究人员能够预测在深层非弹性散射过程中，会产生一系列富中子的不可测量核，其质量数分布在58≤Z≤76之间，这些核的生产截面范围从微博（μb）到毫博（mb）。这表明，154Sm与160Gd的多核子转移反应可能成为合成新一类难以通过传统聚变反应或锕系元素裂变途径获得的富中子镧系元素的有效途径。该研究的重要性在于它扩展了我们对高能核反应的理解，并可能为核物理的前沿探索提供新的可能性，特别是在核合成领域。同时，使用这两种不同的微观动力学模型进行对比分析，对于验证和改进现有理论模型具有显著价值。未来的研究可能会进一步探索这类反应的优化条件和机制，以便于在实验室条件下实现对新核素的可控合成。

Physics Letters B 760 (2016) 236–241

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

New neutron-rich isotope production in

154

Sm+

160

Ning Wang

a,∗

, Lu Guo

b,c

Department of Physics, Guangxi Normal University, Guilin 541004, People’s Republic of China

School of Physics, University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China

State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China

a r t i c l e i n f o a b s t r a c t

Article history:

Received

12 May 2016

Received

in revised form 28 June 2016

Accepted

28 June 2016

Available

online 1 July 2016

Editor:

W. Haxton

Deep inelastic scattering in

154

Sm+

160

Gd at energies above the Bass barrier is for the ﬁrst time

investigated with two different microscopic dynamics approaches: improved quantum molecular

dynamics (ImQMD) model and time dependent Hartree–Fock (TDHF) theory. No fusion is observed from

both models. The capture pocket disappears for this reaction due to strong Coulomb repulsion and the

contact time of the di-nuclear system formed in head-on collisions is about 700 fm/c at an incident

energy of 440 MeV. The isotope distribution of fragments in the deep inelastic scattering process is

predicted with the simulations of the latest ImQMD-v2.2 model together with a statistical code (GEMINI)

for describing the secondary decay of fragments. More than 40 extremely neutron-rich unmeasured

nuclei with 58 ≤ Z ≤ 76 are observed and the production cross sections are at the order of μbto mb. The

multi-nucleon transfer reaction of Sm+Gd could be an alternative way to synthesize new neutron-rich

lanthanides which are diﬃcult to be produced with traditional fusion reactions or ﬁssion of actinides.

(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP

1. Introduction

The heavy-ion reaction at energies around the Coulomb bar-

rier

is an important way not only for the study of the nuclear

structures, but also for the synthesis of unstable or even exotic

(neutron-rich, neutron-deﬁcient, superheavy) nuclei for which no

experimental data exist [1–8]. For light and intermediate fusion

systems, the fusion process is usually described by the penetra-

tion

of the fusion barriers. The fusion (capture) cross sections can

be accurately predicted by using the fusion coupled channel cal-

culations

or empirical barrier distribution approaches [9–14]. For

fusion systems leading to the synthesis of super-heavy elements,

the quasi-ﬁssion and fusion–ﬁssion process signiﬁcantly compli-

cates

the description of fusion process. The very shallow capture

pockets in such kind of reaction systems may cause some diﬃ-

culties

in the applications of the barrier-penetration approaches.

Although macroscopic dynamics models [15–19] met with some

success for describing the residual evaporation cross sections of

measured super-heavy systems, the uncertainty of the predicted

fusion probability from these different models for unmeasured sys-

tems

is still large due to the uncertainty of model parameters

Corresponding author.

E-mail

addresses: wangning@gxnu.edu.cn (N. Wang), luguo@ucas.ac.cn (L. Guo).

[20,21] and ambiguity of reaction mechanism. For example, with

the fusion-by-diffusion model, Choudhury and Gupta [22] investi-

gated

symmetric heavy-ion reaction of

154

Sm+

154

Sm and obtained

measurable evaporation residue cross sections (∼ 0.6pb). How-

ever,

Cap et al. [23] investigated the same reaction and found the

cross sections are extremely small (about 10

−13

pb) and proba-

bly

never reachable. The contradictory predictions imply some key

model parameters such as the injection point distance and the

dynamical nucleus–nucleus potential are far from clear for this re-

action.

It is therefore necessary to investigate the dynamics process

and fusion probability in this kind of reactions with self-consistent

microscopic dynamics models.

addition to the formation of superheavy nuclei, the syn-

thesis

of extremely neutron-rich heavy nuclides through multi-

fragmentation,

deep inelastic scattering and quasi-ﬁssion are of

exceptional importance to advance our understanding of nuclear

structure at the extreme isospin limit of the nuclear landscape

[24–28]. Neutron-rich lanthanides, such as

182

112

with “false

magic numbers”, are of importance for understanding the strength

of spin–orbit interaction which inﬂuences the positions of the

island of stability for super-heavy nuclei. Unfortunately, if one

glances at the chart of nuclides (see the positions of known nuclei

in AME2012 [29]), one notes that the number of observed neutron-

rich

nuclides is very limited at mass region A > 160, due to that

http://dx.doi.org/10.1016/j.physletb.2016.06.073

0370-2693/

SCOAP

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