High-spin yrast structure of159Ho

An investigation of the yrast structure of the odd-$Z$ ${}^{159}$Ho nucleus to high spin has been performed. The ${}^{159}$Ho nucleus was populated by the reaction ${}^{116}$Cd(${}^{48}$Ca,$p4n\ensuremath{\gamma}$) at a beam energy of 215 MeV, and resulting $\ensuremath{\gamma}$ decays were detected by the Gammasphere spectrometer. The ${h}_{11/2}$ yrast band has been significantly extended up to ${I}^{\ensuremath{\pi}}=75/{2}^{\ensuremath{-}}$ (tentatively $79/{2}^{\ensuremath{-}}$). A lower frequency limit for the second ${({h}_{11/2})}^{2}$ proton alignment was extracted consistent with the systematics of this alignment frequency, indicating an increased deformation with neutron number in the Ho isotopes. The energy-level splitting between the signature partners in the ${h}_{11/2}$ structures of the Ho isotopes and the neighboring $N=92$ isotones is discussed.