Nonequilibrium Excitation-Energy Division in Deeply Inelastic Collisions

The division of the excitation energy between the projectilelike and targetlike fragment was measured for $^{56}\mathrm{Fe}$ + $^{238}\mathrm{U}$ at $8.5A$ MeV incident energy. The excitation energy in the heavy fragment was determined from the mass asymmetry of fission fragments coincident with projectilelike fragments. For total energy losses between 30 and 70 MeV the excitation energy is found to divide more nearly equally than predicted by thermal-equilibrium models and is in good agreement with expectations based on nucleon-exchange models.