Influence of the compound-nucleus lifetime on the observed width of hot giant dipole resonances

We discuss the fact that the total width of the photo-absorbtion peak must contain twice the evaporation width of the hot nucleus. Indeed, the observed γ-rays are related with transitions between two levels of the compound nucleus which have a width due to the finite lifetime of the system. This novel physical effect must be taken into account in the discussion of the properties of the photo-absorbtion strength. We discuss how it modifies the predicted total width of giant resonances at moderate excitation energy and we stress that it may play a role in the observed suppression of the GDR at high excitation energy.