Rare decay modes of fission fragments

The experimental data on rare modes of radioactive decay of fission fragments is reviewed. These decay modes are due to a large excess of neutrons and a high energy of β decay fragments. They appear in delayed emission of various particles after the β decay (several neutrons, α particles, or heavy clusters) and excitation of unusual states (giant multipole resonances and shape isomers). The β decay and internal conversion of γ radiation into bound states of the atomic electron shell and their influence on the probability of secondary particle emission are considered. The possibility is discussed of observing decays that have not yet been experimentally detected, but theoretically predicted, as well as information on the nuclear structure obtained by studying such decay modes.