Effects of thermal fluctuations on giant dipole resonances in hot rotating nuclei

Abstract

We present a macroscopic approach to giant dipole resonance (GDR) in highly excited nuclei, using a unified description of quadrupole shape thermal fluctuations. With only two free parameters, which are fixed by the zero-temperature nuclear properties, the-model reproduces well experimental GDR cross sections in the 100 ≤ A ≤ 170 mass range for both spherical and deformed nuclei. We also investigate the cross-section systematics as a function of both temperature and angular velocity and the sensitivity of the GDR peak to the nuclear shape. We conclude that at low temperatures ( T ≈ 1 MeVfs) the GDR cross section is sensitive to changes in the nuclear energy surface. Higher-temperature ( T ≳ 2 MeV) cross sections are dominated by large fluctuations (triaxial in particular) and are much less sensitive to the equilibrium shape.