PHYSICAL REVIEW C 101, 044313 (2020)
New level scheme and shell model description of
212
Rn
C. B. Li (),
1
G. L. Zhang () ,
2, 3 , *
C. X. Yuan (),
4
G. X. Zhang (),
5, 6
S. P. Hu (),
7
W. W. Qu (),
8
Y. Zheng (),
1
H. Q. Zhang (),
1
D. Mengoni,
5, 6
D. Testov,
5, 6
J. J. Valiente-Dobón,
9
H. B. Sun (),
7
N. Wang (),
7
X. G. Wu (),
1
G. S. Li (),
1
M. Mazzocco,
5, 6
A. Gozzelino,
9
C. Parascandolo,
10
D. Pierroutsakou,
10
M. La Commara,
10, 11
F. Recchia,
5, 6
A. I. Sison,
9
S. Bakes,
9
I. Zanon,
9
S. Aydin,
12
and D. Bazzacco
5, 6
1
China Institute of Atomic Energy, Beijing 102413, China
2
School of Physics, Beihang University, Beijing 100191, China
3
Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, School of Medicine and Engineering,
Beihang University, Beijing, 100191, China
and Key Laboratory of Big Data-Based Precision Medicine (Beihang University),
Ministry of Industry and Information Technology, Beijing 100191, China
4
Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, Zhuhai 519082, China
5
Dipartimento di Fisica e Astronomia dell’Universita di Padova, I-35131 Padova, Italy
6
Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova, Italy
7
College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
8
School of Radiation Medicine and Protection, Medical College of Soochow University, Soochow 215123, China
9
INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italy
10
INFN-Sezione di Napoli, via Cintia, I-80126 Napoli, Italy
11
Dipartimento di Farmacia, Università di Napoli “Federico II”, via D. Montesano, I-80131 Napoli, Italy
12
Department of Physics, University of Aksaray, 68100 Aksaray, Turkey
(Received 28 November 2019; accepted 24 March 2020; published 20 April 2020)
Level structures of
212
Rn have been studied by in-beam γ -ray spectroscopic methods using the
209
Bi(
6
Li,
3n)
212
Rn reaction at beam energies of 28, 30, and 34 MeV. A number of new nonyrast states based on π h
4
9/2
and π h
3
9/2
f
7/2
configurations have been identified. A 3
(−)
collective state is also proposed at 2121 keV, which is
most likely formed by mixing the octupole vibration with the 3
−
member of the π h
3
9/2
i
13/2
multiplet. The level
scheme is compared with large-scale shell model calculations and discussed in terms of excitations of valence
protons and without contributions from the
208
Pb core. An overall excellent agreement is obtained for states that
can be described in this model space.
DOI: 10.1103/PhysRevC.101.044313
I. INTRODUCTION
For many years, the spherical nuclei near the doubly closed
shell nucleus
208
82
Pb
126
have provided a laboratory in the heavy-
element region in which the large-scale shell model had been
confronted by experiment [1,2]. Therefore, it is particularly
important to have complete experimental data in this mass
region. A large amount of information on nuclei near
208
Pb
has been obtained through a wide variety of experiments.
Nevertheless, there are many gaps in the data.
The nucleus
212
Rn, with its relatively simple structure
of a closed neutron core, has four valence protons outside
the doubly closed shell
208
Pb core, provides a convenient
system of nuclei for testing the study of both low- and high-
spin states, and has received much attention in the past few
decades. The first study [3,4] of the high-spin level structure of
212
Rn used the
204
Hg(
13
C, 5n)
212
Rn reaction to establish the
basic structure of the nucleus to an excitation energy of about
*
zgl@buaa.edu.cn
8.5 MeV, some involving double neutron core excitations.
Afterwards, a number of isomers and high-lying γ -ray tran-
sitions were observed [5–7]. Recently, Dracoulis et al. [8,9],
using the
204
Hg(
13
C, 5n)
212
Rn and the
198
Pt(
18
O4n)
212
Rn
reactions, extended the level scheme to higher spin (39¯ h),
with an excitation energy in excess of 13 MeV, covering
states formed by aligned valence protons combined with
single, double, and triple neutron-core excitations. These were
interpreted in terms of both the empirical shell model (ESM)
and the deformed independent particle model (DIPM). Life-
times, g-factors and magnetic moments were also measured
by different groups and interpreted them in terms of diverse
microcosmic model [4,10–13,15]. To sum up, previous studies
of the in-beam γ -ray spectroscopy have provided some details
on the energies and decay characteristics of intermediate-high
spin states in
212
Rn. However, these studies have produced no
information at all about the levels of π h
2
9/2
f
2
7/2
configuration,
for the π h
3
9/2
f
7/2
and π h
3
9/2
i
13/2
configurations with J 6,
the data are inadequate or nonexistent, and particularly there
is absence of the extremely interesting collective 3
−
state.
Therefore, much more low-lying information is needed about
2469-9985/2020/101(4)/044313(10) 044313-1 ©2020 American Physical Society