γ-ray spectroscopy of neutron-rich
Sb isotopes beyond 132Sn
J. Keatings
University of the West of Scotland
Motivations
• Sb nuclei very interesting – testing neutron-proton part of effective interaction
outside a 132Sn core.
• Nuclei have simple structure of just a few protons and neutrons outside
closed core – perfect for testing shell model interactions.
• Study of r-process nuclei.
• Data on Sb nuclei essential to optimise the effective interaction, allowing
properties of nuclei not experimentally accessible to be reliably calculated.
137Sb 138Sb 139Sb
>13 neutrons from last stable
Sb nucleus (123Sb). Just
beyond N=82 shell gap.
No excited states known
beyond 136Sb.
Variation between energy predictions of rescaled, empirical, and realistic shellmodel calculations
Proposal submitted to RIKEN PAC: Study of the isomeric
and β-decays of 132Cd and 136,138Sn, G.S. Simpson
Astrophysical r-process
Occurs after core collapse of type-II
supernovae (some debate..).
High neutron flux
Produces ~1/2 of matter in the
universe heavier than Fe.
Nuclear structure properties
(masses, b-decay lifetimes)
determines path taken.
Measuring r-process sensitivity
Brett et al. tested 3 global mass-model
predictions and altered parameters to see
each nucleus’ influence on the abundances.
“The nuclei with greatest impact on the rprocess - neutron-rich isotopes of cadmium,
indium, tin, and antimony in the N = 82 region...”
S. Brett et al., Eur. Phys. J. A. (2012)
BigRIPS & ZeroDegree Spectrometer
345-MeV/u 238U beam
(provided by RRC, fRC,
IRC, SRC) illuminating
Be target.
Measures ΔE, ToF and
Bρ on an event-by event
basis to determine Z and
A/q.
Utilises position
sensitive PPACs, plastic
scintillation counters &
MUSIC.
4𝜋𝑒 4 𝑍 2
2𝑚0 𝑣 2
2 − 𝛽2
Δ𝐸 =
𝑁𝑧
ln
−
ln
1
−
𝛽
𝑚0 𝑣 2
𝐼
N. Fukuda et al., Nucl. Instr. Meth. B. (2013)
Wide Angle Silicon-Strip Stopper Array for
β and Ion detection
8 layered position sensitive
DSSSD
highly segmented (60x40)
14400 1-mm2 pixels
Ions implanted into
WAS3ABI after
leaving ZDS.
~60 ions/s implanted.
G. Lorusso et al., API Confr. Proc. (2013)
EUroball-RIKEN Cluster Array
12 HPGe detectors,
each with 7 crystals.
Detects γ rays from
implanted products
decaying inside
WAS3ABI.
Placed around WAS3ABI
in close geometry, get as
close to 4π coverage.
β-delayed neutron emission
Need a method of separating
different decay modes to
build level schemes.
P. Hoff et al., Phys. Rev. C. (1997)
T1/2 Measurements
Nucleus
This work
[ms]
G. Lorusso et. al.
Phys. Rev. Let.
(2015) [ms]
ENSDF
Value [ms]
130Cd
130(2)
127(2)
162(7)
130In
283(16)
284(10)
290(2)
132In
200(2)
198(2)
207(6)
134Sn
825(78)
890(20)
1050(110)
135Sn
513(6)
515(5)
530(20)
136Sn
355(5)
350(5)
250(30)
137Sn
254(38)
230(30)
190(60)
138Sn
151(33)
140(30)
>408 ns
Summary
• Area near doubly magic
132Sn
very important in
understanding neutron rich nuclear structure.
•
have been populated by β and β-n decay, and
preliminary level schemes have been built.
136,137,138Sb
• Need to carry out shell model predictions for these nuclei
and compare to experimental results.
• Half-lives have been measured for various nuclei near
132Sn.
There is good agreement with accepted values,
apart from 136Sn.
Thank you for your attention.
Collaborators:
G.S. Simpson, A. Jungclaus, J. Taprogge, G. Gey, S. Nishimura,
P. Doornenbal, G. Lorusso, P.-A. Söderström, T. Sumikama, Z.Y. Xu,
H. Baba, F. Browne, N. Fukuda, N. Inabe, T. Isobe, H.S. Jung,
D. Kameda, G.D. Kim, Y.-K. Kim, I. Kojouharov, T. Kubo, N. Kurz,
Y.K. Kwon, Z. Li, H. Sakurai, H. Schaffner, Y. Shimizu, H. Suzuki,
H. Takeda, Z. Vajta, H. Watanabe, J. Wu, A. Yagi, K, Yoshinaga,
S. Böing, J.-M. Daugas, F. Drouet, R. Gernhäuser, S. Ilieva, T. Kröll,
A. Montaner-Pizá, K. Moschner, D. Mücher, H. Nishibata,
A. Odahara, R. Orlandi, K. Steiger, A. Wendt