Dynamical dipole mode in fusion reactions with exotic nuclear beams

We report the properties of the prompt dipole radiation, produced via a collective bremsstrahlung mechanism, in fusion reactions with exotic beams. We show that the $\gamma$ yield is sensitive to the density dependence of the symmetry energy below/around saturation. Moreover, we find that the angular distribution of the emitted photons from such fast collective mode can represent a sensitive probe of its excitation mechanism and of fusion dynamics in the entrance channel.