Fragment emission time scale in intermediate energy heavy ion collisions

Complete two-fragment velocity systematics have been measured over the entire range of fragmentation products for the system $^{56}\mathrm{Fe}$ ${+}^{197}$Au at 50 and 100 MeV per nucleon. Fragment emission lifetimes are estimated from the reduced velocity (${\mathit{V}}_{\mathrm{rel}}$/ \ensuremath{\surd}${\mathit{Z}}_{1}$+${\mathit{Z}}_{2}$ ) correlation functions by a direct comparison with results from a classical three-body trajectory calculation. Furthermore, we examine the validity of the reduced velocity, ${\mathit{V}}_{\mathrm{red}}$, as a scaling parameter for constructing mixed-fragment (${\mathit{Z}}_{1}$\ensuremath{\ne}${\mathit{Z}}_{2}$) correlation functions over the full measured range (5\ensuremath{\le}${\mathit{Z}}_{\mathit{i},}$j\ensuremath{\le}53) of fragment pairs excluding fission.