Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 47 (2014)

Structure of neutron-rich Zr and Mo isotopes
T. Sumikama,∗1,∗3 F. Browne,∗2,∗3 A. M. Bruce,∗2 I. Nishizuka,∗1,∗3 S. Nishimura,∗3 P. Doornenbal,∗3G. Lorusso,∗3 Z. Patel,∗3,∗4 S. Rice,∗3,∗4 L. Sinclair,∗3,∗5 P.-A. Söderström,∗3 H. Watanabe,∗3,∗6 J. Wu,∗3,∗7Z. Y. Xu,∗3,∗8 A. Yagi,∗3,∗9 H. Baba,∗3 N. Chiga,∗1 R. Carroll,∗4 R. Daido,∗3,∗9 F. Didierjean,∗10 Y. Fang,∗3,∗9G. Gey,∗3,∗11,∗12 E. Ideguchi,∗13 N. Inabe,∗3 T. Isobe,∗3 D. Kameda,∗3 I. Kojouharov,∗14 N. Kurz,∗14 T. Kubo,∗3S. Lalkovski,∗15 Z. Li,∗7 R. Lozeva,∗10 N. Fukuda,∗3 H. Nishibata,∗3,∗9 A. Odahara,∗9 Zs. Podolyàk,∗4
P. H. Regan,∗4 O. J. Roberts,∗2 H. Sakurai,∗3,∗8 H. Schaffner,∗14 G. S. Simpson,∗11 H. Suzuki,∗3 H. Takeda,∗3M. Tanaka,∗3,∗13 J. Taprogge,∗3,∗16,∗17 V. Werner,∗18 and O. Wieland∗19
Neutron-rich isotopes in the vicinity of 110 Zr haveattracted much attention, because a shape transition
to oblate or triaxial and a tetrahedral-shape isomer
may be observed.1) The decay spectroscopy of the Zr
and Mo isotopes was performed at RIBF at RIKEN
Nishina Center to extend the previous experiment1)
to more neutron-rich region. The neutron-rich nuclei
were produced by the in-flight-fission reaction of 238 U
beam at 345 MeV/u in a 3-mm-thick Be target, andimplanted into the double-sided silicon-strip detectors(WAS3ABi), which were placed at the center of thehigh-purity-germanium detector array (EURICA).2) A
fast-timing LaBr3 (Ce) array was combined with EURICA for a half-life measurement of excited states.
Figure 1 shows the particle-identification (PID) plotof the radioactive-isotope (RI) beam separated by theBigRIPS separator. The β-γ spectroscopy of 102,104 Y,
and 106 Nb was performed individually by using a highpurity-beam setting. Figure 2 shows the PID spectrumof 102 Y setting. The purity of 102 Y was 46%. A preliminary result of the half-life measurement for 102,104 Zr
using the fast timing array is given in another report.3)
The beam setting shown in Fig. 3 is used to search for
an isomeric state in 110 Mo using a passive Cu stopper.
Further analysis is in progress.

44Z4240
3836

2.65

2.7

A/ Q

2.75

2.8

Fig. 1. PID plot of the atomic number Z and the mass
to charge ratio A/Q. A wider and more-neutron-richregion than Figs. 2 and 3 was selected by the BigRIPS
separator.
4140

Z

3938
102

3736

Y

2.55

2.6

2.65

A/ Q

2.7

2.75

Fig. 2. PID plot of a high-purity-beam setting for the spectroscopic study of β decay from 102 Y.
44∗1Department of Physics, Tohoku University
School of Physics and Nuclear Energy Engineering, University of Brighton∗3 RIKEN Nishina Center∗4 Department of Physics, University of Surrey∗5 Department of Physics, University of York∗6 School of Computing Engineering and Mathematics, Beihang University∗7 Department of Physics, Peking University∗8 Department of Physics, University of Tokyo∗9 Department of Physics, Osaka University∗10 IPHC/CNRS and University of Strasbourg∗11 LPSC, Universitè Grenoble-Alpes, CNRS/IN2P3∗12 ILL, Grenoble∗13 RCNP, Osaka University∗14 GSI∗15 Department of Physics, Sofia University∗16 Departamento de Fı́sica Teórica, Universidad Autónoma deMadrid∗17 Institutode Estructura de la Materia∗18 Department of Physics, Yale University∗19 INFN Sezione di Mirano

110∗2MoZ42

40

38

2.6

2.65

A/ Q

2.7

2.75

Fig. 3. PID plot of a high-purity-beam setting to search for
an isomeric state in 110 Mo.

References
1) T. Sumikama et al.: Phys. Rev. Lett. 106, 202501 (2011).
2) S. Nishimura: Prog. Theor. Exp. Phys. 2012 03C006.
3) F. Browne et al.: RIKEN Accel. Prog. Rep. 47, (2014).

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