Isospin symmetry in B(E2) values: Coulomb excitation study of 21Mg

P. Ruotsalainen*, J. Henderson, G. Hackman, G.H. Sargsyan, K.D. Launey, A. Saxena, P.C. Srivastava, S.R. Stroberg, T. Grahn, J. Pakarinen, G.C. Ball, R. Julin, P.T. Greenlees, J. Smallcombe, C. Andreoiu, N. Bernier, M. Bowry, M. Buckner, R. Caballero-Folch, A. ChesterS. Cruz, L.J. Evitts, R. Frederick, A.B. Garnsworthy, M. Holl, A. Kurkjian, D. Kisliuk, K.G. Leach, E. McGee, J. Measures, D. Mücher, J. Park, F. Sarazin, J.K. Smith, D. Southall, K. Starosta, C.E. Svensson, K. Whitmore, M. Williams, C.Y. Wu

*Corresponding author for this work

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The Tz = -3/2 nucleus 21Mg has been studied by Coulomb excitation on 196Pt and 110Pd targets. A 205.6(1)-keV γ-ray transition resulting from the Coulomb excitation of the 5/2+ ground state to the first excited 1/2+ state in 21Mg was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the 1/2+ state yield an adopted value of B(E2;5/2+→1/2+)=13.3(4) W.u. A new excited state at 1672(1) keV with tentative 92+ assignment was also identified in 21Mg. This work demonstrates a large difference in the B(E2;5/2+→1/2+) value between T=3/2, A=21 mirror nuclei. The difference is investigated in the shell-model framework employing both isospin conserving and breaking USD interactions and using modern ab initio nuclear structure calculations, which have recently become applicable in the sd shell.
Original languageEnglish
Article number051301
JournalPhysical Review C
Issue number5
Publication statusPublished - 6 May 2019
Externally publishedYes


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