Doorway thermodynamics of pre-equilibrium nuclear reactions

The slowest nuclear reactions are those that proceed through a thermally equilibrated intermediate state of overlapping resonances. In addition to the thermalized particles, pre-equilibrium reaction products are also observed to boil off from earlier stages of the reaction, providing evidence of an equilibration process that leads from an initial ''hot spot'' in phase space to the equilibrated compound system. The finite-nucleus process of equilibration has been given an elegant description in terms of doorway-state to doorway-state transitions, and it is this equilibration model that is reviewed here. (author)