Off-shell effects in (d,p) stripping reactions and the three body system

The importance of off-shell effects was investigated in (d,p) stripping reactions and the model triton. For the stripping reactions a formalism is developed for calculating differential cross sections and angular distributions assuming a direct process. By taking into account the off-shell background term and its interference, several levels in the reaction 15N(d,p)16N are interpreted. Contributions to the resonances from other sources are considered by extending the coupled channel theory off the energy shell. In three soluble two-channel models with square well, delta-function and non-local interactions the off-shell resonance and bound state behaviour is discussed. The off-shell T-matrix for nuclear reactions is also derived using the R-matrix theory. For the model triton the ground state energy for two classes of potentials have been calculated. These potentials fit the low energy data and also support a continuum bound state (CBS). In each class two sets of potentials, one with a continuum bound state at K = 5 fm-1 and the other at K = 7 fm-1 have been investigated. The rank two potentials produce a triton ground state collapse in all cases. The binding increases as the CBS moves to higher energies and decreases when the repulsive form factor becomes stronger. The partly non-local potentials combine long-range locality with a short-range non-locality. Though their non-local parts acting alone produce a collapse, no collapse has been found for the total interaction. The binding is almost the same as that of the local potential acting alone