A superdeformed band has been found in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Eu}$. It is populated with 1.2(2)% of the total γ-ray intensity that decayed into ${}_{}{}^{142}{}_{}{}^{}\mathrm{Eu}$ via the reaction ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$${(}^{27}$Al,5n${)}^{142}$Eu at 152 MeV. The strength of the band is similar to that previously reported in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$, where the superdeformed band is populated with an intensity of 1.1(1)%. This is unexpected, since both total Routhian surface (TRS) and cranked modified oscillator (MO) calculations predict that the superdeformed band in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ becomes yrast at lower spin than that in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Eu}$. This difference is ∼4ħ in the MO calculations and ∼8ħ in the TRS. Extrapolation of the ‘‘normal’’-deformed yrast states in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Eu}$ shows, however, that a difference of ∼8ħ in spin corresponds to a change in the relative energy of the superdeformed and normal-deformed yrast lines of only ∼1 MeV.

• Received 16 March 1995

DOI:https://doi.org/10.1103/PhysRevC.52.99