Preequilibrium Reactions with Complex Particle Channels

Existing phenomenological models for direct reactions in the continuum with complex particles in the exit and/or entrance channels have been substantially revised. These models supplement the exciton preequilibrium model and a standard evaporation model in providing a coherent and complete description of experimental energy spectra. The description for nucleon-induced reactions is reasonably complete, but additional work for incident complex particles is needed to properly include the effects of projectile breakup (fragmentation). The present work indicates the importance of allowing for the excitation of extra particle-hole pairs during nucleon transfer; it supports previous systematics with regard to the surface localization of neutron-induced reactions; and it provides insights into key exciton model parameters for complex projectiles. For most of these reactions, direct nucleon transfer is the dominant direct reaction mechanism, while for inelastic channels the consideration of cluster scattering seems important.