Evidence for Thermal Equilibration in Multifragmentation Reactions   probed with Bremsstrahlung Photons
  The production of nuclear bremsstrahlung photons (E$_{\gamma}>$ 30 MeV) has been studied in inclusive and exclusive measurements in four heavy-ion reactions at 60{\it A} MeV. The measured photon spectra, angular distributions and multiplicities indicate that a significant part of the hard-photons are emitted in secondary nucleon-nucleon collisions from a thermally equilibrated system. The observation of the thermal component in multi-fragment $^{36}$Ar+$^{197}$Au reactions suggests that the breakup of the thermalized source produced in this system occurs on a rather long time-scale. 
D.G. d'Enterria, L. Aphecetche, A. Chbihi, H. Delagrange, J. D\'iaz,   M.J. van Goethem, M. Hoefman, A. Kugler, H. L\"ohner,...