Excited superdeformed bands have been observed in the N=86 isotones ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Tb}$. The properties of these bands were found to closely resemble those of the yrast superdeformed bands in their Z+1 N=86 isotones ${(}^{151}$Tb and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Dy}$) such that, on average, the transition energies are identical to an accuracy of 1:1000. It is proposed that these excited superdeformed bands are based on single-proton excitations from the [301]1/2 orbital into the [651]3/2 intruder orbital and thus they are the first obsrevation of proton excitations in superdeformed nuclei.

• Received 18 December 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.1650