GDR dissipation and nuclear shape in hot fast-rotating Dy nuclei

Abstract The statistical γ-ray decay of the GDR built on excited states in Dy nuclei has been investigated for selected domains of angular momentum up to about 70ħ and temperatures in the range 1–2 MeV. The GDR strength distribution extracted from the data indicate large average nuclear deformations ( β ∼ 0.35) at high angular momentum and average temperatures T ⩾ 1.5 MeV. The experimental observation is supported by results from calculations in which thermal shape fluctuations are taken into account around an oblate equilibrium deformation β eq . Although this equilibrium deformation increases with angular momentum, the calculations show rather large and constant average deformations 〈 β ∼0.35.