The multifragmentation freeze-out volume in heavy-ion collisions

Reduced velocity correlation functions for fragments from the reaction Fe+Au at 100 A MeV bombarding energy are investigated using the dynamical-statistical approach QMD+SMM. It is shown that such a two-step model can consistently explain the data if a simultaneous multifragmentation with a freeze-out volume corresponding to 0.1-0.3 times normal nuclear matter density is used. The calculations show an additional correlation due to recoil effects from a third heavy fragment in an asymmetric break-up. This effect is present, but less pronounced in the data.