Identifying the spin trapped character of the ${}^{32}$Si isomeric state

Abstract

The properties of a nanosecond isomer in ${}^{32}$Si, disputed in previous studies, depend on the evolution of proton and neutron shell gaps near the `island of inversion'. We have placed the isomer at 5505.2(2) keV with $J^{\pi }=5^{-}$, decaying primarily via an $E3$ transition to the $2_1^{+}$ state. The $E3$ strength of 0.0841(10) W.u. is unusually small and suggests that this isomer is dominated by the $(\nu d_{3/2}{)}^{-1}\otimes (\nu f_{7/2}{)}^1$ configuration, which is sensitive to the $N=20$ shell gap. A newly observed $4_1^{+}$ state is placed at 5881.4(13) keV; its energy is enhanced by the $Z=14$ subshell closure. This indicates that the isomer is located in a `yrast trap', a feature rarely seen at low mass numbers.

arXiv commentAccepted, Physical Review C

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Cited by in corpus (1)

• Intruder structures in ${}^{32}$Si and ${}^{29}$Al