A Band Crossing Model of Resonances in Heavy Ion Reactions. I: Resonances in 12C-16O Scattering

Abstract

A band crossing model, which has been recently proposed by the present authors for an occurrence mechanism of resonances in heavy ion reactions, is explained in detail. The model is based on the observations (a) that prominent resonances are realized correlately among channels on the condition that resonances in inelastic or rearrangement channels locate close to those in the incident channel with the same spins and parities, and (b) that an aligned band, where the spin of (an excited state of) interacting nuclei and the orbital angular momentum of the relative motion between them are parallel to give the maximum total spin, usually crosses with the potential resonance band in the incident channel. By inspecting the crossing diagram together with the tops of the barrier heights of the total potential, we can predict where and with what spins molecular resonances appear with a certain nuclear configuration. The model is applied to the resonances observed well above the Coulomb barrier in the ¹²C-¹⁶O system. Characteristic features of the elastic excitation function with rather sharp resonances are well reproduced and at the same time the doublet-like resonances in the inelastic excitation function are excellently well explained by an interplay among the potential resonance band in the elastic channel and the aligned rotational band in the collectively excited inelastic channels. Characteristic consequences of the model are given, together with a semi-quantitative prediction as to a role of the excitation of the α-cluster states in ¹⁶O.