Intruder Configurations in theA=33Isobars:Mg33andAl33

• DOI: 10.1103/physrevlett.101.142504
• Publication Date: 2008-10-02T16:14:38Z
• Authors: Vandana Tripathi; S. L. Tabor; P. F. Mantica; Y. Utsuno; P. Bender; J. Cook; C. R. Hoffman; Sangjin Lee; T. Otsuka; J. Pereira; M. Perry; K. Pepper; J. S. Pinter; J. Stoker; A. Volya; D. Weisshaar
• Keywords: 0103 physical sciences; 01 natural sciences

The $\ensuremath{\beta}$ decay of $^{33}\mathrm{Mg}$ ($N=21$) presented in this Letter reveals intruder configurations in both the parent and the daughter nucleus. The lowest excited states in the $N=20$ daughter nucleus, $^{33}\mathrm{Al}$, are found to have nearly $2p\ensuremath{-}2h$ intruder configuration, thus extending the ``island of inversion'' beyond Mg. The allowed direct $\ensuremath{\beta}$-decay branch to the $5/{2}^{+}$ ground state of the daughter nucleus $^{33}\mathrm{Al}$ implies positive parity for the ground state of the parent $^{33}\mathrm{Mg}$, contrary to an earlier suggestion of negative parity from a $g$-factor measurement. An admixture of $1p\mathrm{\text{\ensuremath{-}}}1h$ and $3p\mathrm{\text{\ensuremath{-}}}3h$ configurations is proposed for the ground state of $^{33}\mathrm{Mg}$ to explain all of the experimental observables.