The dynamical dipole mode in dissipative heavy-ion collisions

We study the effect of a direct giant dipole resonance (GDR) excitation in intermediate dinuclear systems with exotic shape and charge distributions f ormed in charge asymmetric fusion entrance channels. A related enhancement of the GDR gamma yield in the evaporation cascade of the fused nucleus is e xpected. The dynamical origin of such GDR extra strength will show up in a characteristic anisotropy of the dipole gamma-emission. A fully microscopic analysis of the fusion dynamics is performed with quantitative predictions of the GDR photon yield based on a dynamics-statistics coupling model. In particular we focus our attention on the energy and mass dependence of the effect, We suggest a series of new experiments, in particular some optimal entrance channel conditions. We stress the importance of using the new avai lable radioactive beams, (C) 2001 Elsevier Science B.V. All rights reserved .