Identification of theKπ=8−rotational band in138Gd

Abstract

A ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ collective rotational band has been established upon the 6 $\ensuremath{\mu}$s isomeric state in the very neutron-deficient nucleus ${}^{138}\mathrm{Gd}.$ The band was observed using a technique involving the correlation of $\ensuremath{\gamma}$-ray transitions across the isomeric state. The single-particle configuration of the isomer has been deduced from the $\ensuremath{\Delta}I=2$ to $\ensuremath{\Delta}I=1$ intensity branching ratios. In addition, a series of other $\ensuremath{\gamma}$-ray transitions were observed which are reasoned to be part of a higher-lying four quasiparticle structure which decays through the ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ isomeric state. The properties of the ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ band are discussed in relation to the systematic properties of ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ bands in the neighboring $N=74$ isotones.