<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>Z</mml:mi> <mml:mo>=</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> </mml:math> Magicity Revealed by the Mass of the Proton Dripline Nucleus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi>Si</mml:mi> </mml:mrow> <mml:mprescripts/> <mml:none/> <mml:mrow> <mml:mn>22</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:mrow> </mml:math>
Y. M. Xing, Ying-she Luo, Y. H. Zhang, M. Wang, X. H. Zhou, J. G. Li, K. H. Li, Qiong Yuan, Y. Niu, Jian-You Guo, Junchen Pei, F. R. Xu, G. de Angelis, Yu. A. Litvinov, K. Blaum, I. Tanihata, Takayuki Yamaguchi, Yang Yu, Xuan Zhou, Han‐Shu Xu, Z. Y. Chen, Rui Jiu Chen, Heng‐Ning Deng, Chuancheng Fu, Wenwei 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, Youjin Yuan, M. Zhang
Abstract
Using the Bρ-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_{2p}=+1412(114)/+229(54) keV, fixing the proton dripline location for the Si element. By analyzing the mass differences of the neighboring sd-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 π2s_{1/2} orbital.