Salient features of scattering amplitudes in intermediate energy nucleon-nucleus scattering

Phenomenological relativistic optical models for scattering of nucleons from a spin-0 nucleus mainly use two different approaches. In the first, one essentially uses the Schrödinger equation incorporating appropriate relativistic kinematical terms. In the second approach, which is superior especially in reproducing spin observables, one starts with the Dirac equation and obtains an equivalent Schrödinger equation which forms a convenient basis for the calculation of experimental observables. Adopting a mathematical procedure developed earlier within the framework of potential scattering, we calculate the regionwise contribution to the reaction cross section for spin-1/2-spin-0 systems using both these types of relativistic optical models. The relative importance of different regions of intermediate energy optical potential in generating the total reaction cross section is examined using the method of regionwise absorption and it is found that reaction process is surface dominant. These findings are further elaborated by depicting the general features of S matrix and scattering amplitudes as a function of angular momentum.