Article révisé par les pairs
Résumé : Some new experimental data are discussed in the framework of a previously proposed model with one single Regge pole. These data show that as opposed to the forward case, the backward elastic scattering depends critically on the microscopic properties of the projectile and the target nucleus. Our model reproduces perfectly the results obtained by Van Oers et al. for α-16O; for α-12C scattering in the 20-23 MeV region, a normalization factor must be introduced to take care of the considerable amount of absorption in the states which give most of the backward contribution. The physical interpretation of the pole as a temporary rotator with a very short lifetime leads to dimensions compatible with the basic hypotheses of the model. On comparing the one-pole formulae for the spin 0 spin 0 and spin 0 spin 1 2 cases, a striking qualitative difference is found in the large angle elastic scattering, heavy oscillations in the first case and no oscillations in the second. Both show however a large peak in the extreme backward scattering. The present data for α-31P confirm this prediction. A conclusive test would be to compare the backward elastic scattering of 4He and 3He by the same even nucleus at the same energy in the barycentric system. © 1966.