Nuclear molecular resonances

Abstract

This article is intended as a review of the status of our understanding of the phenomena of nuclear molecular resonances observed in heavy-ion collisions. It also surveys the experimental data in this field, and the various models, and theories proposed so far to describe them. The inability, and the inadequacies of the conventional description using frozen optical potentials have been analysed. An claborate account of the recently developed Dynamic Potential Model is presented. In this model, the nuclear molecular resonances are described in terms of rotational and vibrational excitations similar to those observed in diatomic molecules. The combination of a Morse type potential and a constant is shown to represent the effective potential between two ions, whose parameters are determined from the resonance data themselves. The important new feature of this potential is that it has a very long range, of about 15 fm. The bound and resonance states of this potential can account for most of the resonances, in a given system. Applications of this model to 12 C+ 12 C, 16 O+ 16 O, 12 C+ 16 O, α+ 12 C and α+ 16 O show its general validity. The very long range nature of the effective potential determined here, and evidences from nuclear structure, deep inelastic and fusion studies give the mechanism of these resonances in which, two highly prolate deformed ions form a diatomic-like nuclear molecule inside a thick Coulomb barrier, and generate rotation-vibration spectrum in the final phase of the reaction in the exit channel.