Quenching of photon decay in hot giant dipole resonances

The quenching of photon decays in giant dipole resonances (GDR) at high excitation energy (E^*) is explained as due to the competition between γ-ray and particle emission. This effect is related to a large increase of the GDR width with the temperature of the nucleus in presence of a pre-equilibrium mechanism that also tends to reduce the collective dipole strength. A saturation of the GDR width at high excitation energy cannot account for the experimental data. Limiting temperatures for the observation of GDR γ-decays are deduced. The E^*-dependence of photon yields above the GDR region is also discussed.