Decay Properties of Giant Multipole Resonances: Collective Doorways and Statistical Doorways

A theoretical framework for the description of the decay of giant multipole resonances is developed. It is shown that the statistical decay of the giant resonances is not necessarily described by the Hauser-Feshbach theory because of the existence of a mixing parameter. The contribution of preequilibrium emission to the giant-resonance decay is also discussed. Application is made to the decay of the giant monopole resonance of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$.