Resonances and off-shell characteristics of effective interactions

The importance of including experimental resonances in constructing effecti ve intercluster interactions has been investigated. For this, we first addr ess the question of how to obtain the analytical properties of the Jest fun ction in regions of physical interest on the complex k-plane when the poten tial is given in a tabular form. We then employ the Marchenko inverse scatt ering method to construct, numerically, phase equivalent local potentials s upporting the same bound state(s) but having different resonance spectra wh ich affect the off-shell characteristics of the corresponding scattering am plitudes. This implies that the inclusion of the experimental resonances in constructing a potential would change its shape, strength, and range which in turn would modify the bound and scattering wave functions in the interi or region. This is expected to have important consequences in calculations of transition amplitudes in nuclear reaction theories, which strongly depen d on the behaviour of the wave functions at short distances. The influence of Supersymmetric Transformations on the position and movement of resonance s has also been investigated. (C) 1999 Elsevier Science B.V. All rights res erved.