First high-precision direct determination of the atomic mass of a superheavy nuclide

P. Schury; T. Niwase; M. Wada; P. Brionnet; S. Chen; T. Hashimoto; H. Haba; Y. Hirayama; D. S. Hou; S. Iimura; H. Ishiyama; S. Ishizawa; Y. Ito; D. Kaji; S. Kimura; H. Koura; J. J. Liu; H. Miyatake; J.-Y. Moon; K. Morimoto; K. Morita; D. Nagae; M. Rosenbusch; A. Takamine; Y. X. Watanabe; H. Wollnik; W. Xian; S. X. Yan

doi:10.1103/PhysRevC.104.L021304

Letter

First high-precision direct determination of the atomic mass of a superheavy nuclide

P. Schury ^1,*, T. Niwase^1,2,3, M. Wada¹, P. Brionnet³, S. Chen^4,1, T. Hashimoto⁵, H. Haba³, Y. Hirayama¹, D. S. Hou^6,7,8 et al.

S. Iimura^9,3,1, H. Ishiyama³, S. Ishizawa^10,3,†, Y. Ito^11,3,1, D. Kaji³, S. Kimura³, H. Koura¹¹, J. J. Liu^4,1, H. Miyatake¹, J.-Y. Moon⁵, K. Morimoto³, K. Morita^2,12, D. Nagae¹², M. Rosenbusch¹, A. Takamine³, Y. X. Watanabe¹, H. Wollnik¹³, W. Xian^4,1, and S. X. Yan¹⁴

¹KEK Wako Nuclear Science Center, Wako, Saitama 351-0198, Japan
²Department of Physics, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
³RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198, Japan
⁴Department of Physics, The University of Hong Kong, Pokfulam 999077, Hong Kong
⁵Institute for Basic Science, 70, Yuseong-daero 1689-gil, Yusung-gu, Daejeon, Korea
⁶Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
⁷University of Chinese Academy of Sciences, Beijing 100049, China
⁸School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
⁹Department of Physics, Osaka University, Osaka, Japan
¹⁰Graduate School of Science and Engineering, Yamagata University, Yamagata, Japan
¹¹Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan
¹²Research Center for SuperHeavy Elements, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
¹³New Mexico State University, Las Cruces, New Mexico 88001, USA
¹⁴Institute of Mass Spectrometer and Atmospheric Environment, Jinan University, Guangzhou 510632, China

^*schury@post.kek.jp
^†Present address: Yoshikawa Laboratory, Institute for Materials Research (KINKEN, IMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.

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Phys. Rev. C 104, L021304 – Published 31 August, 2021

DOI: https://doi.org/10.1103/PhysRevC.104.L021304

Abstract

We present the first direct measurement of the atomic mass of a superheavy nuclide. Atoms of ${}^{257}{Db}$ ( $Z = 105$ ) were produced online at the RIKEN Nishina Center for Accelerator-Based Science using the fusion-evaporation reaction ${}^{208}{Pb} ({}^{51}V$ , 2n) ${}^{257}{Db}$ . The gas-filled recoil ion separator GARIS-II was used to suppress both the unreacted primary beam and some transfer products, prior to delivering the energetic beam of ${}^{257}{Db}$ ions to a helium gas-filled ion stopping cell wherein they were thermalized. Thermalized ${}^{257}{Db}^{3 +}$ ions were then transferred to a multireflection time-of-flight mass spectrograph for mass analysis. An alpha particle detector embedded in the ion time-of-flight detector allowed disambiguation of the rare ${}^{257}{Db}^{3 +}$ time-of-flight detection events from background by means of correlation with characteristic $α$ decays. The extreme sensitivity of this technique allowed a precision atomic mass determination from 11 events. The mass excess was determined to be $100 063 {(231)}_{stat} {(132)}_{sys} keV / c^{2}$ . Comparing to several mass models, we show the technique can be used to unambiguously determine the atomic number as $Z = 105$ and should allow similar evaluations for heavier species in future work.

Physical Review C

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First high-precision direct determination of the atomic mass of a superheavy nuclide

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