Evolution of the decay modes of 158Yb with spin

The decay of the entry states in 158Yb populated in the reactions of 149 MeV 20Ne with 144,146Nd has been investigated with the Spin Spectrometer gated by a Ge counter. The average excitation energy, the γ-ray spectra and the angular distributions as a function of multiplicity suggest a region of non-collective behavior at low spin. At higher spin collective characteristics are apparent, but between I≈40 and 49 a strong stretched dipole component is seen. Above I≈49 no additional dipole transitions are observed. These characteristics are discussed in terms of recent calculations.