Strong population of a superdeformed band in Eu142

A superdeformed band has been found in Eu142. It is populated with 1.2(2)% of the total γ-ray intensity that decayed into Eu142 via the reaction Sn120(27Al,5n)142Eu at 152 MeV. The strength of the band is similar to that previously reported in Eu143, 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 Eu143 becomes yrast at lower spin than that in Eu142. This difference is ∼4ħ in the MO calculations and ∼8ħ in the TRS. Extrapolation of the ‘‘normal’’-deformed yrast states in Eu143 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.