PHYSICAL REVIEW C 93, 034324 (2016)
Structure of
132
52
Te
80
: The two-particle and two-hole spectrum of
132
50
Sn
82
S. Biswas,
1
R. Palit,
1
A. Navin,
2
M. Rejmund,
2
A. Bisoi,
3
M. Saha Sarkar,
4
S. Sarkar,
3
S. Bhattacharyya,
5
D. C. Biswas,
6
M. Caama˜ no,
7
M. P. Carpenter,
8
D. Choudhury,
1
E. Cl´ ement,
2
L. S. Danu,
6
O. Delaune,
2
F. Farget,
2
G. de France,
2
S. S. Hota,
9
B. Jacquot,
2
A. Lemasson,
2
S. Mukhopadhyay,
6
V. Nanal,
1
R. G. Pillay,
1
S. Saha,
1
J. Sethi,
1
Purnima Singh,
1
P. C. Srivastava,
10
and S. K. Tandel
11
1
Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai 400005, India
2
GANIL, CEA/DRF - CNRS/IN2P3, Bd Henri Becquerel, BP 55027, F-14076 Caen Cedex 5, France
3
Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India
4
Saha Institute of Nuclear Physics, I/AF Bidhan Nagar, Kolkata 700064, India
5
Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700064, India
6
Bhabha Atomic Research Centre, Mumbai 400085, India
7
USC, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain
8
Argonne National Laboratory, Argonne, Illinois 60439, USA
9
Australian National University, Canberra ACT2601, Australia
10
Department of Physics, Indian Institute of Technology, Roorkee 247667, India
11
UM-DAE Centre for Excellence in Basic Sciences, Mumbai 400098, India
(Received 30 October 2015; revised manuscript received 26 February 2016; published 21 March 2016)
High-spin states in
132
Te, an isotope with two proton particles and two neutron holes outside of the
132
Sn
doubly magic core, have been extended up to an excitation energy of 6.17 MeV. The prompt-delayed coincidence
technique has been used to correlate states above the T
1/2
= 3.70(9) μs isomer in
132
Te to the lower states using
232
Th(
7
Li ,f ) at 5.4 MeV/u and the Indian National Gamma Array (INGA). With
9
Be(
238
U ,f ) at 6.2 MeV/u
and EXOGAM γ -array coupled with the VAMOS++ spectrometer, the level scheme was extended to higher
excitation energies. The high-spin positive-parity states, above J
π
= 10
+
, in
132
Te are expected to arise from
the alignment of the particles in the high-j orbitals lying close to the Fermi surface, the πg
2
7/2
, and the νh
−2
11/2
configurations. The experimental level scheme has been compared with the large scale shell model calculations.
A reduction in the p-n interaction strength resulted in an improved agreement with the measurements up to the
spin of 15. In contrast, the comparison of the differences between the experiment and these calculations for the
N = 76,78 isotones of Te and Sn shows the increasing disagreement as a function of spin, where the magnitude
is larger in Te than in Sn. This behavior could possibly be attributed to the deficiencies in the p-n correlations,
in addition to the n-n correlations in Sn.
DOI: 10.1103/PhysRevC.93.034324
I. INTRODUCTION
The predictivity of large scale shell model calculations
based on modern effective interactions [1,2] for nuclei around
132
Sn is a topic of current interest in nuclear structure [3–8].
This is motivated by the recent availability of high quality
γ -ray spectroscopic data for neutron-rich nuclei in this mass
region from a number of experiments using a variety of
techniques [9–13]. The goal of the comparison of the results
of large scale shell model calculations with the experimental
data is to develop methods to derive a more reliable effective
nucleon-nucleon interaction required to understand: (i) the
mechanism of shell migration and modifications of shell gaps
as a function of isospin [14], (ii) the p-n correlations [15]
as function of spin and isospin in addition to the better
studied n-n and p-p correlations. At higher spin, the in-
teractions between the protons and neutrons can be studied
while they align simultaneously. A basic building block for
studying all the correlations consists of a pair of protons and
neutrons interacting with each other. Thus the development
of collectivity can be studied with increasing number of
active particles. In this regard, the Te isotopic chain with
N 82 having two proton particles and several neutron holes,
spanning a large number of isotopes that are accessible, is ideal
and in particular,
132
Te that contains a pair of protons and
neutrons.
The structure of
132
Te was experimentally studied only
up to the 10
+
and 7
−
seniority isomers, typical in this
mass region [16–18]. Level structures of
124–131
Te have been
recently reported up to high-spin using fusion-fission reactions
from triple γ -coincidence data [19] using EUROBALL.
132
Te
was populated in the β decay of
132
Sb [20,21],
7
Li +
130
Te
fusion evaporation reaction [22], and by thermal neutron
induced fission of
239
Pu and
241
Pu [23]. The yrast band has
been extended to 10
+
level, which is an isomeric state with a
half-life of 3.70(9) μs[23]. Here we report new results from
two complementary experiments establishing an extended
level structure of
132
Te. In the first experiment, two γ rays
above the 3.70(9) μs isomer in
132
Te have been established
in coincidence with the delayed γ -rays emitted from the
states below the isomer using
232
Th(
7
Li ,f ) at 5.4 MeV/u
with INGA at Tata Institute of Fundamental Research (TIFR).
The level structure of
132
Te has been further extended up
to 6.17 MeV excitation energy using
9
Be(
238
U ,f ) reac-
tion at 6.2 MeV/u beam energy in EXOGAM-VAMOS++
set up at Grand Acc´ el´ erateur National d’Ions Lourds
(GANIL).
2469-9985/2016/93(3)/034324(8) 034324-1 ©2016 American Physical Society