Quantum-mechanical approaches to continuum angular distributions

Starting with the introduction of the exciton model by Griffin in 1966, a series of semiclassical models of varying complexities has been developed for calculating and evaluating particle emissions in the continuum. It was also shown that with some freedom in the choice of parameters, these models can give reasonable fit to the observed energy and angular distributions of the emitted particles. More recently, researchers have formulated several quantum-mechanical reaction theories that are based on multistep concepts and in which statistical evaporation at lower energies is connected to direct reactions at higher energies. The subject of this paper is these quantum-mechanical theories, with emphasis on their formal differences, calculational complexities, and predictive powers for nucleon-induced reactions below 100 MeV. The semiclassical theories are not included