Surfaces waves in α-nuclei elastic scattering

A theory of surface waves, excited by the grazing rays in the elastic scattering of α particles on nuclei, working within the framework of the short wavelenght appoximation is developed. The nuclear interaction region is schematized as an absorbing sphere surronded by a nearly transparent shell; the surfaces waves, wich are excited at the edge of the interaction region and propagate along it, can take one or more shortcuts. In this way we can explain the large angle elastic scattering of α particles on 16O, 28Si and 40Ca from approx.20 to approx.60 MeV. Indeed the theory is tested by fitting the differential cross sections of these scattering processes. The nuclear interaction radii can be extracted from phenomenological analysis