RIKEN Accel. Prog. Rep. 50 (2017)

Ⅱ-1. Nuclear Physics

β-decay γ-ray spectroscopy of 140 Te : level structure of 140 I beyond
N = 82
B. Moon,∗1 C.-B. Moon,∗2 A. Odahara,∗3 R. Lozeva,∗4 C. Yuan,∗5 P.-A. Söderström,∗6 F. Browne,∗6
H. S. Jung,∗7 P. Lee,∗8 C. S. Lee,∗8 A. Yagi,∗3 S. Nishimura,∗6 P. Doornenbal,∗6 G. Lorusso,∗6 H. Watanabe,∗6I. Kojouharov,∗9 T. Sumikama,∗6 T. Isobe,∗6 H. Baba,∗6 H. Sakurai,∗6 R. Daido,∗3 Y. Fang,∗3 H. Nishibata,∗3Z. Patel,∗10 S. Rice,∗10 L. Sinclair,∗11 J. Wu,∗6 Z. Y. Xu,∗12 R. Yokoyama,∗13 T. Kubo,∗6 N. Inabe,∗6H. Suzuki,∗6 N. Fukuda,∗6 D. Kameda,∗6 H. Takeda,∗6 D. S. Ahn,∗6 Y. Shimizu,∗6 D. Murai,∗14
F. L. Bello Garrote,∗15 J. M. Daugas,∗6∗16 F. Didierjean,∗5 E. Ideguchi,∗3 T. Ishigaki,∗3 S. Morimoto,∗3M.Niikura,∗6 I. Nishizuka,∗17 T. Komatsubara,∗6 Y. K. Kwon,∗18 and K. Tshoo∗1844.0
51.4
56.0
102.0
77.0
121.0
142.4
134.2
185.6
113.8
229.4
234.5
342.1351.9
382.6
497.0
620.3
722.3
734.7
790.6
645.4
830.0
198.1
435.2
583.3
739.8
783.3
804.9
817.8
875.0
925.9

952.9
1046.71067.11136.41187.91551.61601.11644.81787.2

The region beyond the doubly-magic nucleus 132 Sn
is currently the subject of great experimental and theoretical interest in view of the shell structure evolution and rapid neutron capture processes. An accurate
measurement of the β-decay of neutron-rich nuclei iscrucial for the determination of the r-process path. We
report the ﬁrst observation of excited states of 140 I by
the β-delayed γ-ray spectrosocopy of 140 Te.
The 140 Te nuclide was produced by the in-ﬂight ﬁssion with a 345 MeV per nucleon 238 U primary beam
on a 9 Be target by means of the BigRIPS separator.
A total of 1.8×106 ions of 140 Te was implanted during the beam time among about 107 total implantedions. After beams were implanted on the active doubleside stripped silicon detector array, WAS3ABi, γ-rays
following after the β-decay were detected by Euroball
RIKEN HPGe Cluster Array(EURICA) surrounding
WAS3ABi.1,2)
Total 40 γ-rays were assigned as internal transitionsof 140 I. The level scheme of 140 I as shown in Fig. 1 has
been built based on γγ coincidence matrices and theβ-delayed γ-ray singles spectrum. The β-decay halflife of the parent 140 Te was obtained to be 350(5) ms
by the 341-, 739-, 875-keV transitions.
Spin parity assignments of the established levels
were made on the basis of the logf t value argument.
For instance, those with logf t values of near 6 to 7, applying to the region of the ﬁrst forbidden β strengths,

1786.91187.9
925.9
881.4
842.0
727.7
639.4
490.0
459.4
342.0
234.8
185.6
142.4
121.0
107.4
51.4
44.0
5.40Fig. 1. The level scheme of 140 I. The thickness of each transition represents the relative intensity to the 44 keVtransition.

are possibly 0, 1, and 2. We note that the spin-parity of
the ground state should be assigned as (2− ) according
to our analysis of the β-decay to 140 Xe. The 5.4-keVlevel is likely to be a (1− ) state based on the shellmodel calculations. Additionally, levels with a directtransition to the ground state are assigned as (1− ) or(2− ) by assuming that all transitions are M1.
The level at 926 keV is assigned as an 1+ state withan argument based on the log ft value, 4.89. This
1+ state is strongly related to the Gamow-Teller(G-T)
transition. In this region, the only allowed β-decaytransitions, G-T transitions, involves the decay of an
h9/2 neutron to an h11/2 proton. Such a decay from aneven-even nucleus gives rise to a [νh9/2 πh11/2 ]1+ statein the odd-odd daughter nucleus.

∗1Department of Physics, Korea University
Department of Display Engineering, Hoseo University∗3 Department of Physics, Osaka University∗4 IPHC, CNRS, IN2P3 and University of Strasbourg∗5 Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University∗6 RIKEN Nishina Center∗7 Agency of Defence Development∗8 Department of Physics, Chung-Ang University∗9 GSI Helmholtzzentrum für Schwerionenforschung GmbH, D64291, Darmstadt, Germany∗10 Department of Physics, University of Surrey∗11 Department of Physics, University of York
∗12 Department of Physics, University of Tokyo∗13 Center for Nuclear Study, University of Tokyo∗14 Department of Physics, Rikkyo University∗15 Department of Physics, University of Oslo
∗16 CEA, DAM, DIF∗17 Department of Physics, Tohoku University∗18 Rare Isotope Science Project, Institute for Basic Science∗2References
1) P.-A. Söderström et al. Nucl. Instrum. Methods Phys.
Res., Sect. B 317, 649 (2013).
2) S. Nishimura, Prog. Theor. Exp. Phys. 2012, 03C006(2012).

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