High precision quadrupole moment measurements of states up to I=20 planck in the yrast band of Er-158

The lifetimes of excited states in the yrast band in ${}^{158}\mathrm{Er}$ up to ${I}^{\ensuremath{\pi}}{=20}^{+}$ have been measured to high precision by means of the Gammasphere spectrometer using the coincidence recoil distance technique. The reaction ${}^{122}\mathrm{Sn}{(}^{40}\mathrm{Ar},4n)$ at a beam energy of 185 MeV was used. The data were analyzed using the differential decay-curve method and transition quadrupole moments were extracted. The quadrupole moment was found to gradually increase by 15% of its ${2}^{+}$ value before the first $\ensuremath{\nu}{i}_{13/2}$ alignment, after which it drops to a constant level 90% of the ${2}^{+}$ value. Detailed comparisons are made with previous measurements and Ultimate Cranker calculations.