<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>Z</mi><mo>=</mo><mn>14</mn></mrow></math> Magicity Revealed by the Mass of the Proton Dripline Nucleus <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Si</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>22</mn></mrow></mmultiscripts></mrow></math>

Y. M. Xing; Y. F. Luo; Y. H. Zhang; M. Wang; X. H. Zhou; J. G. Li; K. H. Li; Q. Yuan; Y. F. Niu; J. Y. Guo; J. C. Pei; F. R. Xu; G. de Angelis; Yu. A. Litvinov; K. Blaum; I. Tanihata; T. Yamaguchi; Y. Yu; X. Zhou; H. S. Xu; Z. Y. Chen; R. J. Chen; H. Y. Deng; C. Y. Fu; W. W. Ge; W. J. Huang; H. Y. Jiao; H. F. Li; T. Liao; J. Y. Shi; M. Si; M. Z. Sun; P. Shuai; X. L. Tu; Q. Wang; X. Xu; X. L. Yan; Y. J. Yuan; M. Zhang

doi:10.1103/ffwt-n7yc

$Z = 14$ Magicity Revealed by the Mass of the Proton Dripline Nucleus ${}^{22}{Si}$

Y. M. Xing ^1,2,*, Y. F. Luo ^1,2,*, Y. H. Zhang ^1,2,†, M. Wang ^1,2, X. H. Zhou^1,2, J. G. Li ^1,2,3,‡, K. H. Li^1,4, Q. Yuan¹, Y. F. Niu ^5,6 et al.

J. Y. Guo⁷, J. C. Pei ⁸, F. R. Xu ^8,3, G. de Angelis ^9,1,§, Yu. A. Litvinov ^10,11, K. Blaum ¹², I. Tanihata ^13,14, T. Yamaguchi ¹⁵, Y. Yu^1,2, X. Zhou¹, H. S. Xu^1,2, Z. Y. Chen^1,2, R. J. Chen ^1,10, H. Y. Deng^1,2, C. Y. Fu¹, W. W. Ge¹, W. J. Huang ^16,1, H. Y. Jiao^1,2, H. F. Li¹, T. Liao ^1,2, J. Y. Shi^1,2, M. Si¹, M. Z. Sun¹, P. Shuai¹, X. L. Tu^1,2, Q. Wang¹, X. Xu ^1,2, X. L. Yan^1,2, Y. J. Yuan ^1,2, and M. Zhang ¹

¹State Key Laboratory of Heavy Ion Science and Technology, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
²School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
³Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences, Huizhou 516000, China
⁴Institute of Particle and Nuclear Physics, Henan Normal University, Xinxiang 453007, China
⁵School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
⁶Frontiers Science Center for Rare Isotope, Lanzhou University, Lanzhou 730000, China
⁷School of Physics and Optoelectronic Engineering, Anhui University, Hefei 230601, China
⁸State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China
⁹INFN Laboratori Nazionali di Legnaro, viale dell’Università 2 Legnaro, Italy
¹⁰GSI Helmholtzzentrum für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany
¹¹Institut für Kernphysik, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
¹²Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
¹³School of Physics, Beihang University, Beijing 100191, China
¹⁴Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki Osaka 567-0047, Japan
¹⁵Department of Physics, Saitama University, Saitama 338-8570, Japan
¹⁶Advanced Energy Science and Technology Guangdong Laboratory, Huizhou 516007, China

^*These authors contributed equally to this work.
^†Contact author: yhzhang@impcas.ac.cn
^‡Contact author: jianguo_li@impcas.ac.cn
^§Contact author: giacomo.deangelis@lnl.infn.it

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Phys. Rev. Lett. 135, 012501 – Published 2 July, 2025

DOI: https://doi.org/10.1103/ffwt-n7yc

Abstract

Using the $B ρ$ -defined isochronous mass spectrometry technique, we conducted the first mass measurement of the proton dripline nucleus ${}^{22}{Si}$ . We confirm that ${}^{22}{Si}$ is bound against particle emission with $S_{p} / S_{2 p} = + 1412 (114) / + 229 (54) keV$ , fixing the proton dripline location for the Si element. By analyzing the mass differences of the neighboring $s d$ -shell nuclei, we find that ${}^{22}{Si}$ exhibits a doubly magic character similar to its mirror partner ${}^{22}O$ , and that the mirror energy difference of ${}^{22}{Si} − {}^{22}O$ deviates from the predictions assuming mirror symmetry. Gamow shell-model calculations reveal that the average occupations of valence protons in ${}^{22}{Si}$ are nearly identical to those of valence neutrons in ${}^{22}O$ , supporting the $Z = 14$ magicity in ${}^{22}{Si}$ . The observed mirror-symmetry breaking is attributed to the extended proton distribution in ${}^{22}{Si}$ arising from a small contribution of the unbound $π 2 s_{1 / 2}$ orbital.

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$Z = 14$ Magicity Revealed by the Mass of the Proton Dripline Nucleus ${}^{22}{Si}$

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Z=14 Magicity Revealed by the Mass of the Proton Dripline Nucleus Si22

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$Z = 14$ Magicity Revealed by the Mass of the Proton Dripline Nucleus ${}^{22}{Si}$