par Michel, Francis;Ohkubo, Shigeo;Reidemeister, Guy
Référence Progress of theoretical physics. Supplement, 132, page (7-72)
Publication Publié, 1998
Article révisé par les pairs
Résumé : We review the merits of the local potential approach in the description of elastic alpha-particle scattering and of alpha-cluster structure in medium-weight nuclei. We recall how optical model analyses of elastic scattering angular distributions, displaying an anomalous large angle enhancement, yielded unique optical potentials, whose real part is determined with good accuracy up to small internucleus distances, and we investigate their properties; we then analyze the general compatibility of these potentials with the microscopic requirements resulting from the constraints due to antisymmetrization, in the case of a system which was thoroughly investigated from a microscopic point of view, and whose spectroscopy is well agreed upon, that is, the 20Ne = α + 16O system. The local potential approach is then applied to the 44Ti = α + 40Ca system - which is the analogue of 20Ne in the fp-shell -whose α-cluster spectroscopy remained unclear for a long time and for which microscopic calculations led to contradictory interpretations; not only does this simple model give a nice account of the energy location and intraband electromagnetic transition probabilities for the members of the 44Ti ground state band, but it predicts the existence of excited alpha-cluster bands, which were subsequently identified experimentally in alpha-transfer experiments. The same approach is applied to the 40Ca = α + 36Ar system, where similar predictions have recently been confirmed experimentally, and to other systems close to the sd-shell closure region. Finally the persistence of alpha-cluster structure in medium-weight and heavy nuclei is discussed within the local potential approach.