六零镍中揭示的手性双峰现象与全量子模型研究

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本文主要探讨了在轻质偶数核$^{60}$Ni中可能存在的一种未解决的问题——手性双峰现象，特别是在M1和M4两个磁矩能级上。研究者采用了最新的全量子四j壳三轴粒子转子模型来深入分析这一现象。该模型能够精确模拟核内的复杂运动，并且在处理角动量和空间定向方面具有较高的准确性。作者J.Penga和Q.B.Chen来自北京师范大学物理系和德国慕尼黑工业大学物理系，他们合作进行了这项研究。他们的工作重点是重现实验观测到的$^{60}$Ni的能量谱、双峰之间的能量差以及磁矩转换率比（B(M1)/B(E2)）等关键参数。通过细致的理论计算和分析，包括对角动量分量的考察、方位角图的解析以及K曲线的研究，他们发现手性模态在M1和M4双峰中的存在概率显著增加，特别是对于角动量量子数I大于或等于12ħ的情况。手性双峰的存在与否，对于理解核结构中的手性对称性及其对核力和核反应的影响至关重要。这一发现不仅有助于核物理学家进一步深化对核结构的认识，也可能在核反应动力学、核天体物理学等领域产生新的理论预测和实验指导。由于文章是开放获取的，意味着研究结果可以被广泛地查阅和讨论，促进学术界的交流与合作。本文的成果为解决$^{60}$Ni中手性双峰问题提供了强有力的支持，并展示了量子力学在描述核内部复杂运动方面的强大能力。未来的研究可能会沿着这个方向继续探索其他类似现象，以揭示更多关于原子核手性特性的新信息。

Physics Letters B 793 (2019) 303–307

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Possible chiral doublets in

J. Peng

a,∗

, Q.B. Chen

Department of Physics, Beijing Normal University, Beijing 100875, China

Physik-Department, Technische Universität München, D-85747 Garching, Germany

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

Article history:

Received

26 December 2018

Received

in revised form 20 April 2019

Accepted

26 April 2019

Available

online 2 May 2019

Editor:

W. Haxton

The open problem on whether or not the chirality exists in doublet bands M1 and M4 in light-mass

even-even nucleus

Ni is studied by adopting the recently developed fully quantal four- j shells triaxial

particle rotor model. The corresponding experimental energy spectra, energy differences between doublet

bands, and the available B(M1)/B(E2) values are successfully reproduced. The analyses on the basis of

the angular momentum components, the azimuthal plots, and the K -plots suggest that the chiral modes

exist at I ≥ 12

h in doublet bands M1 and M4.

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

Nuclear chiral rotation is an exotic form of spontaneous sym-

metry

breaking, which exists only in nucleus with triaxial ellip-

soidal

shape. In 1997, Frauendorf and Meng proposed that the total

angular momentum vector of a rotating triaxial nucleus may lie

outside the three principal planes in the intrinsic frame. Such an

angular momentum geometry can, in the laboratory frame, give

rise to a pair of nearly degenerate I = 1 bands with the same

parity, i.e., chiral doublet bands [1]. So far, more than 50 chiral

candidates have been reported in odd-odd, odd- A, and even-even

nuclei that spread over A ∼ 80 [2], 100 [3–10], 130 [11–21], and

190 mass regions [22,23]. For more details, see reviews [24–29]

and

very recent data tables [30].

During

the process of investigating nuclear chirality, exploring

novel chiral phenomena and searching for new chiral candidates

are the two fundamental goals all the time. For the former, e.g., the

multiple chiral doublets (Mχ D) phenomenon, i.e., having multiple

pairs of chiral doublet bands in a single nucleus, was theoretically

predicted and explored by the state-of-art covariant density func-

tional

theory (CDFT) [31–37] and observed in

133

Ce [38],

103

[39],

Br [40],

136

Nd [41,42], and

195

Tl [43]. These observations

conﬁrm the existence of triaxial shapes coexistence [31,38,41,43],

and reveal the stability of chiral geometry against the increasing

of intrinsic excitation energy [39,44–47] and octupole correlations

[40]. For the latter, the experimental evidence of chiral doublet

bands was ﬁrst observed in the A ∼ 130 mass region, and then

followed by the A ∼100, 190, and 80 mass regions. These observa-

tions

show that the nuclear chirality is not a speciﬁc phenomenon

that exists in only one nucleus or one mass region.

Corresponding author.

E-mail

addresses: jpeng@bnu.edu.cn (J. Peng), qbchen@pku.edu.cn (Q.B. Chen).

Both of the two fundamental goals and all of relevant obser-

vations

mentioned above encourage us to search for new candi-

dates

with chirality or Mχ D in new mass regions. In Ref. [37],

we explored the Mχ D in A ∼ 60 mass region by the adiabatic

and conﬁguration-ﬁxed constrained CDFT for cobalt isotopes. It

was found that there are high- j particle(s) and hole(s) conﬁgura-

tions

with prominent triaxially deformed shapes in these isotopes,

which suggests the possibility of chirality or multiple chirality in

A ∼ 60 mass region. However, the experimental energy spectra

and electromagnetic transition in these isotopes are rather rare at

present.

note that in Ref. [48], the fully microscopic self-consistent

tilted axis cranking covariant density functional theory (TAC-CDFT)

was applied to investigate the observed dipole bands M1, M2, M3,

and M4 in even-even nucleus

Ni [49]. It was mentioned that

bands M1 and M4 might be the possible candidates for chiral dou-

blet

bands. However, due to the mean-ﬁeld approximation, the TAC

can only give the description for the band M1. After that, there

is neither further theoretical nor experimental work to investigate

bands M1 and M4 in

Ni. Therefore, whether the chirality exists

in the bands M1 and M4 or not is still an open problem.

The

aim of the present work is to investigate the chirality in

doublet bands M1 and M4 in

Ni in a fully quantal model. As

a quantal model coupling the collective rotation and the single-

particle

motions, the particle rotor model (PRM) has been widely

used to describe the chiral doublet bands and achieved major suc-

cesses

[24]. In contrast to the TAC approach, PRM describes a sys-

tem

in the laboratory frame. The total Hamiltonian is diagonalized

with total angular momentum as a good quantum number, and

the energy splitting and quantum tunneling between the doublet

bands can be obtained directly. Moreover, the basic microscopic

https://doi.org/10.1016/j.physletb.2019.04.065

0370-2693/

SCOAP

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