THE ANGULAR-MOMENTUM DEPENDENCE OF THE GIANT-DIPOLE RESONANCE IN DY-154

Abstract The statistical γ-ray decay of the compound nucleus 154 Dy ∗ formed at an excitation energy of 69 MeV is studied in three angular-momentum windows 〈 J 〉 = 31,42 and 50ℏ. The GDR strength function extracted from the data indicates a constant centroid energy for the resonance E GDR = 15.2 ± 0.5 MeV, a small deformation of the nuclear shape for all spin regions and an increase in the resonance width with increasing angular momentum. The latter might indicate larger shape fluctuations at higher angular momenta. A systematical study of the dependence of the extracted strength function with different methods of analysis is presented, and their discrepancies discussed.