Multistep processes in nuclear reactions

Recent applications of the theory of Feshbach, Kerman and Koonin to analyse multistep processes in nuclear reactions are described, and illustrated by detailed comparisons with a range of experimental data for neutron and proton reactions. The techniques used to distinguish between the multistep direct, multistep compound, compound and collective contributions to the cross-sections are described, and their effectiveness assessed. Particular attention is devoted to recent analyses that take into account the transitions from the multistep direct to the multistep compound chain and also to those that evaluate the collective contributions to the continuum region. The variation of the effective nucleonnucleon interaction with incident energy and target nucleus is studied, and the possibility of a parameter-free calculation is discussed. The extensions of the theory to include multiparticle emission from the direct chain and also to studies of alpha-particle emission are described.

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