Hard photons: production mechanisms and nuclear dynamics

The occurrence in the photon spectra of a component between 30 and 50 MeV with inverse slope parameter smaller than that expected in the first chance neutron-proton bremsstrahlung hypothesis is studied in Ni-58 + Al-27 at 30A MeV and Ni-58 + Au-197 at 30A and 45A MeV reactions. For the Ni-58 + Au-197 system at 45A MeV the influence of nuclear dynamics on this component is investigated exploiting its correlations with multifragment emission.