Blocking Effect in the Transitional NucleiAu189,191,193

The study of high-spin states in ${}_{}{}^{189,191,193}{}_{}{}^{}\mathrm{Au}$ revealed that the $h_{\frac{11}{2}}$ proton-hole rotation-aligned bands are terminated by isomeric ${\frac{27}{2}}^{-}$ states most probably of ${\left(\pi h_{\frac{11}{2}}^{}{}_{}{}^{-3\mathrm{}}\right)}_{{\frac{27}{2}}^{-}}$ configuration. The relatively low excitation energies of these isomers can be understood qualitatively if the concept of blocking as used in the rotation-alignment model is modified by taking into account a reduction of the proton pairing gap energy in these odd-mass Au nuclei.