Terminating bands were first observed in nuclei around 158Er (Z=68, N=90). At termination, this nucleus can be considered as a 146Gd spherical core plus twelve (4 protons and 8 neutrons) aligned valence particles which generate a spin 46+. These valence particles move in equatorial orbits giving the nucleus an oblate appearance. Work with Eurogam has established other termination states in 158Er at 48- and 49-, and several terminating states in the neighbouring 157Er isotope. An experiment has been performed at GAMMASPHERE in order to measure lifetimes of high-spin states in 157-158Er using the Recoil Distance Method. More recently, a high-fold, high-statistics experiment was carried out with GAMMASPHERE to investigate the feeding of terminating states in these nuclei.
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