Blocking of Octupole Correlations Deduced from the Decay of a Multiparticle Isomer in212At

Abstract

A high spin isomer with spin ${25}^{\ensuremath{-}}$ and mean lifetime of $220\ensuremath{\mu}\mathrm{s}$ has been observed at an excitation energy of 4772 keV in ${}^{212}\mathrm{At}$. The measured $E3$ decay rate for the 224 keV transition deexciting this level is enhanced but significantly lower than those observed in the neighboring isotopes or predicted using a multiparticle octupole coupling model. The relatively simple configurations involved in this decay and the close relationship to neighboring states allow a clear association to be made between the occupation of a specific single particle orbital and a blocking of the octupole vibrational correlation.