The ZD MRTOF system at RIKEN BigRIPS is a new high-precision multi-reflection time-of-flight (MRTOF) mass spectrograph for low-energy radionuclides, which is located downstream of the ZeroDegree spectrometer. A novel helium-filled gas-catcher cell based on radiofrequency (RF) ion guides has been developed to thermalize and transport radioisotopes (RIs) produced via in-flight fission and fragmentation at relativistic energies [1]. The stopped RI ions were extracted from the gas cell as atomic or molecular ions and transported to the MRTOF mass spectrograph [2,3] for direct mass measurements with high resolving power. The first online commissioning experiment was performed in winter 2020. During the commissioning, many atomic masses were measured in a series of parasitic experiments, which provides valuable input for nuclear astrophysics and nuclear structure studies [3]. In this contribution, we would like to report the mass measurement results of Ag, ^{111,113}^{111-113}^{111,112}^{112}Mo. Based on the systematics of two-neutron separation energies(S$_{2n$}) around N = 70, we discuss our results in the context of the sudden onset of nuclear deformation in this region visible by S2n values, which maximizes for Sr, Y, and Zr isotopes [4]. Furthermore, we compare our data with global mass models and present new results from a Bayesian machine-learning approach.
References
[1] M. Wada et al., Nucl. Instrum. Methods Phys. Res. B. 204, 570 (2003).
[2] H. Wollnik and M. Przewloka, Int. J. Mass Spectrom. Ion Proc., 96, 267 (1990).
[3] M. Rosenbusch et al., Nucl. Instrum. Methods Phys. Res. A 1047, 167824 (2023).
[4] S. Naimi et al., Phys. Rev. Lett. 105, 032502 (2010).
Dongsheng Hou
(IMP)
Prof.
Takamine A
(RIKEN Nishina Center)
Dr.
Iimura S
(Department of Physics, College of Science, Rikkyo University)
Dr.
Rosenbusch M
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
Z Liu
(Institute of Modern Physics, Chinese Academy of Sciences)
Dr.
S Chen
(School of Physics, Engineering and Technology, University of York)
Herr
W Xian
(Department of Physics, The University of Hong Kong)
Herr
S Yan
(Jinan University)
Prof.
M Wada
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
P Schury
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
Y Hirayama
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
H Ishiyama
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Dr.
Y Ito
(Advanced Science Research Center, JAEA Ibaraki)
Dr.
S Kimura
(RIKEN Nishina Center)
Prof.
J Lee
(Department of Physics, The University of Hong Kong )
Dr.
J Liu
(Institute of Modern Physics, Chinese Academy of Sciences)
Prof.
H Liang
(Department of Physics, Graduate School of Science, The University of Tokyo)
Prof.
T.M Kojima
(RIKEN Nishina Center)
Prof.
S Mchimasa
(Center for Nuclear Studies (CNS), The University of Tokyo)
Prof.
H Miyatake
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
S Naimi
(RIKEN Nishina Center)
Prof.
S Nishimura
(RIKEN Nishina Center)
Prof.
Z Niu
(School of Physics and Optoelectronic Engineering, Anhui University)
Dr.
T Niwase
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
T Sonoda
(RIKEN Nishina Center)
Prof.
Y.X Watanabe
(Wako Nuclear Science Center (WNSC), IPNS, KEK)
Prof.
H Wollnik
(New Mexico State University)
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