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

Author:

J. Williams, G. Hackman, K. Starosta, R. S. Lubna, Priyanka Choudhary, P. C. Srivastava, C. Andreoiu, D. Annen, H. Asch, M. D. H. K. G. Badanage, G. C. Ball, M. Beuschlein, H. Bidaman, V. Bildstein, R. Coleman, A. B. Garnsworthy, B. Greaves, G. Leckenby, V. Karayonchev, M. S. Martin, C. Natzke, C. M. Petrache, A. Radich, E. Raleigh-Smith, D. Rhodes, R. Russell, M. Satrazani, P. Spagnoletti, C. E. Svensson, D. Tam, F. Wu, D. Yates, Z. Yu

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex)

journal:

date:

2023-11-15 00:00:00

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.

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