Statistical description of the decay of nuclei having two classes of excited states

Abstract

The decay of heavy nuclei is discussed in the framework of the statistical theory using the double-humped model for the fission barrier. It is shown that the existence of two classes of excited states in such nuclei is reflected in many observables, such as the decay law, the cross sections, the partial decay probabilities and the time dependence of decay yields. It is demonstrated that: (i) the decay time in the fission channel is different from that in any other channel; (ii) the partial decay probabilities depend on the initial conditions under which the compound nucleus is formed; (iii) the lifetime of the second-well states influences the evaporation spectra. It is also shown that the decay time characteristics of nuclei having two classes of excited states contain information on the strongly deformed excited states in the second well, like their density, and the depth of the second well itself.