Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 53

TDPAD measurement for the 10− isomer of 98 Y
J. M. Daugas,∗1,∗2,∗3 F. Boulay,∗1,∗2,∗4 Y. Ichikawa,∗2 A. Takamine,∗2 D. S. Ahn,∗2 K. Asahi,∗2,∗5 H. Baba,∗2
D. L. Balabanski,∗2,∗6 T. Egami,∗2,∗7 T. Fujita,∗2,∗8 N. Fukuda,∗2 C. Funayama,∗2,∗5 T. Furukawa,∗2,∗9G. Georgiev,∗10 A. Gladkov,∗2,∗11 M. Hass,∗12 K. Imamura,∗2,∗13 N. Inabe,∗2 Y. Ishibashi,∗2,∗14 T. Kawaguchi,∗2,∗7T. Kawamura,∗8 W. Kim,∗11 Y. Kobayashi,∗15 S. Kojima,∗2,∗5 A. Kusoglu,∗10,∗16 R. Lozeva,∗10 S. Momiyama,∗17I. Mukul,∗12 M. Niikura,∗17 H. Nishibata,∗2,∗8 T. Nishizaka,∗2,∗7 A. Odahara,∗8 Y. Ohtomo,∗2,∗5 D. Ralet,∗10T. Sato,∗2,∗5 G. S. Simpson,∗18 Y. Shimizu,∗2 T. Sumikama,∗2 H. Suzuki,∗2 H. Takeda,∗2 L. C. Tao,2,19
Y. Togano,∗5 D. Tominaga,∗2,∗7 H. Ueno,∗2 H. Yamazaki,∗2 and X. F. Yang∗20
0.20

340

3300

R(t)

0.10
0.05
0-0.05
-0.10
-0.15

0.08

(b) A=7.5(21)%

R(t)

0.04
0-0.04-0.080.15(c)

0.10

2 1

0.05
0-0.05260

Yield (pps/mm)(a) A=17(4)%

0.15

R(t)

A time-diﬀerential perturbed angular distribution(TDPAD) measurement was performed for the 10− isomer 98m Y. The ﬁrst aim of this experiment was to investigate the single-particle structure and on the wave
functions of 98m Y, which is located in a region with arapid change of the ground-state nuclear shape, throughthe magnetic moment. The second aim was to measure
the amount of spin alignment of the isomeric states produced by the abrasion-ﬁssion reaction.
Neutron-rich N = 59 isotones were produced by theabrasion-ﬁssion reaction of a primary 238 U beam at
345 MeV/nucleon incident on a 100-µm-thick 9 Be target. A thin target was used to avoid the mixing of different momentum distributions if the reaction occurredat the entrance or exit of the target. Figure 1 shows thethree selections in the momentum distribution of 98 Y

-0.10
200

220

400

600

800

1000

1200

1400

Time (ns)180Fig. 2. (a), (b), and (c) represent the R(t) ratio of 98m Y forselections 1, 2, and 3, respectively. See Refs. 1–2) for thedefinition of R(t).

1401006020-300-260-220-180-140-100-60-202060100X (mm)Fig. 1. Selections in the momentum distribution ofdistribution shape was estimated by LISE++.

98

Y. The∗1CEA, DAM, DIF
RIKEN Nishina Center∗3 LCM, LNE-CNAM∗4 GANIL, CEA/DSM-CNRS/IN2P3∗5 Department of Physics, Tokyo Institute of Technology∗6 ELI-NP, IFIN-HH∗7 Department of Advanced Sciences, Hosei University∗8 Department of Physics, Osaka University∗9 Department of Physics, Tokyo Metropolitan University∗10 IJCLab, CNRS/IN2P3, Université Paris-Saclay∗11 Department of Physics, Kyungpook National University∗12 Department of Particle Physics, Weizmann Institute of Science∗13 Department of Physics, Meiji University∗14 Department of Physics, University of Tsukuba∗15 Department of Informatics and Engineering, University ofElectro-Communication∗16 Department of Physics, Istanbul University∗17 Department of Physics, University of Tokyo∗18 LPSC, CNRS/IN2P3, Université Grenoble Alpes∗19 School of Physics, Peking University∗20 Instituut voor Kern- en Stralingsfysica, K. U. Leuven∗2- 45 -at F1. The selected isotones were implanted in a nonperturbating copper host at F8. The TDPAD apparatus
located at F8 was same as in Refs. 1–2), and an external
magnetic ﬁeld of 0.250 T was applied.
Figures 2 (a), (b), and (c) show the TDPAD spectrawith respect to the momentum distribution, where thehighest spin alignment of 17(4)% is located in its outerwing and no spin alignment exists at the center. Theg-factor of 98m Y was deduced to be |g| = 0.36(2). Thisvalue is far from the one expected under the assumptionof a (πg9/2 ⊗ h11/2 )10− conﬁguration, where the additivity rules give g = +0.517 considering the g-factorsof the 9/2+ and the 11/2− isomers of 97 Y and 99 Mo,
respectively.3,4) The interpretation of this result needs
improvement in theoretical calculations for the odd-odd
mass isotopes in this interesting region.
References

1) Y. Ichikawa et al., Nature Phys. 15, 321 (2019).
2) F. Boulay et al., Phys. Rev. Lett. 124, 112501 (2020).
3) B. Cheal et al., Phys. Lett. B 645, 133 (2007).
4) J. M. Daugas, private communication.