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R. Orlandi; M. Asai; H. Makii; K. Nishio; K. Hirose; K. Tsukada; T. K. Sato; Y. Ito; F. Suzaki; Y. Nagame; T. Ishii; A. N. Andreyev; K. Okada; Y. Kasamatsu; A. Toyoshima; I. Nishinaka; Y. Ishii; R. Takahashi; E. Ideguchi; N. Aoi; T. T. Pham; H. Haba; D. Kaji; K. Morimoto; Y. Kojima; S. Yan; Y. Shen; B. Gao; G. Li; A. V. Afanasjev

doi:10.1103/7gzt-ldn5

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Deformation and Magicity in Heavy Actinides: First Observation of the Ground-State Rotational Band of ${}^{252}{Fm}$

R. Orlandi ^1,*, M. Asai ¹, H. Makii ¹, K. Nishio ¹, K. Hirose¹, K. Tsukada ^1,2, T. K. Sato ^1,3, Y. Ito ^1,4, F. Suzaki¹ et al.

Y. Nagame ¹, T. Ishii ¹, A. N. Andreyev ^1,5, K. Okada¹, Y. Kasamatsu^1,6, A. Toyoshima^1,7, I. Nishinaka ^1,8, Y. Ishii^1,9, R. Takahashi^1,10, E. Ideguchi ¹¹, N. Aoi¹¹, T. T. Pham ¹¹, H. Haba¹², D. Kaji¹², K. Morimoto ¹², Y. Kojima ^13,14, S. Yan¹⁵, Y. Shen ¹⁵, B. Gao¹⁶, G. Li¹⁶, and A. V. Afanasjev¹⁷

¹Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
²Research Center for Accelerator and Radioisotope Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
³Institute for Integrated Radiation and Nuclear Science, Kyoto University, Kumatori, Osaka 590-0494, Japan
⁴Wako Nuclear Science Center, Institute of Particle and Nuclear Studies, KEK, Wako, Saitama 351-0198, Japan
⁵School of Physics Engineering and Technology, University of York, Heslington, York YO10 5DD, United Kingdom
⁶Department of Chemistry, The University of Osaka, Toyonaka, Osaka 560-0043, Japan
⁷Institute for Radiation Sciences, The University of Osaka, Toyonaka, Osaka 560-0043, Japan
⁸Department of Quantum-Applied Biosciences, National Institutes for Quantum Science and Technology (QST), Takasaki, Gunma 370-1292, Japan
⁹Naka Institute for Fusion Science and Technology, National Institutes for Quantum Science and Technology, Naka, Ibaraki 311-0193, Japan
¹⁰J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
¹¹Research Center for Nuclear Physics (RCNP), The University of Osaka, Osaka 567-0047, Japan
¹²Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0198, Japan
¹³Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
¹⁴Office of Health and Safety, Hokkaido University, Sapporo 060-0808, Japan
¹⁵China Institute of Atomic Energy, Beijing 102413, China
¹⁶Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu 73000, China
¹⁷Department of Physics and Astronomy, Mississippi State University, Mississippi 39762, USA

^*Contact author: orlandi.riccardo@jaea.go.jp

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Phys. Rev. Lett. 137, 082501 – Published 17 August, 2026

DOI: https://doi.org/10.1103/7gzt-ldn5

Abstract

The ground-state rotational band of ${}^{252}{Fm}$ ( $Z = 100$ , $N = 152$ ) was investigated using two different experimental setups at the JAEA Tandem Accelerator Laboratory. The $2^{+} \to 0^{+}$ and $4^{+} \to 2^{+}$ transitions were observed in the $α$ decay of ${}^{256}{No}$ via $α − γ$ coincidence spectroscopy. The energies of the $(6^{+}) \to (4^{+})$ , $(8^{+}) \to (6^{+})$ , and $(1 0^{+}) \to (8^{+})$ transitions were identified in the prompt $γ$ -ray spectrum of ${}^{252}{Fm}$ produced in the ${}^{18}O + {}^{249}{Cf}$ multinucleon transfer reaction. The new data reveal that, compared with neighboring fermium isotopes and $N = 152$ isotones in the region, ${}^{252}{Fm}$ has the lowest first excited $2^{+}$ -state energy, 41.88(16) keV, and the largest kinematic moment of inertia. These properties constitute new evidence for the deformed shell gaps at $Z = 100$ and $N = 152$ , supporting the understanding of ${}^{252}{Fm}$ as a deformed doubly magic nucleus.

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Deformation and Magicity in Heavy Actinides: First Observation of the Ground-State Rotational Band of ${}^{252}{Fm}$

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Deformation and Magicity in Heavy Actinides: First Observation of the Ground-State Rotational Band of Fm252

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Deformation and Magicity in Heavy Actinides: First Observation of the Ground-State Rotational Band of ${}^{252}{Fm}$