The odd-proton ${}_{}{}^{141}{}_{}{}^{}\mathrm{Eu}$ nucleus is studied with the ${}_{}{}^{110}{}_{}{}^{}\mathrm{Cd}$${(}^{35}$Cl,2p2nγ) reaction populating states in seven distinct bands. For the yrast band, high spin states are followed up to ${\mathit{I}}^{\mathrm{\pi }}$=43/$2^{\mathrm{-}}$ and a band crossing, due to the alignment of the second and third ${\mathit{h}}_{11/2}$ protons, is observed at a rotational frequency ħ${\mathrm{\omega }}_{\mathit{c}}$=0.37 MeV. For the positive-parity bands, only the three-quasiparticle configuration, namely, π${\mathit{g}}_{7/2}$⊗[π${\mathit{h}}_{11/2}$${]}^2$, is observed up to high spins. In addition, two ΔI=1 bands with no E2 crossovers are found in this nucleus. The cause of the relatively strong M1 transition bands can be explained by a drastic shape change due to the alignment of an ${\mathit{h}}_{11/2}$ neutron pair. A systematic comparison amongst the N=78 isotones, ${}_{}{}^{137}{}_{}{}^{}\mathrm{Pr}$, ${}_{}{}^{139}{}_{}{}^{}\mathrm{Pm}$, and ${}_{}{}^{141}{}_{}{}^{}\mathrm{Eu}$, is made.

• Received 29 November 1990

DOI:https://doi.org/10.1103/PhysRevC.43.2189