Break-up reactions leading to resonant final states

A theoretical model for knock-out reactions, which leave the residual nucleus in an unbound (resonant) state, has been worked out. The main problem is to describe the motion of a nucleon relative to an unstable core, which through an oscillating potential influences the motion of the nucleon even far away from the core. By a suitable redefinition of the potential, we have succeeded in eliminating some unphysical features of the interaction between the unstable core and the nucleon. In this model the origin of the imaginary part of the potential is well understood and some qualitative features are deduced. For instance it is shown that the imaginary part is positive and predominantly localized at the nuclear surface. This theory has been applied to the reaction 6Li(p,2p)5He. Even in a model where the target nucleus is described schematically our theory gives better fit to experimental data than other calculations. (Auth.)