Assessing the Evolutionary Nature of Multifragment Decay

Multifragment decays of central collisions in ${}^{84}\mathrm{Kr}{+}^{197}\mathrm{Au}$ at $E/A=35\mathrm{}$, 55, and 70 MeV are studied. The dependence of the extracted emission time on the velocity of the fragment pair is investigated. More energetic pairs manifest a stronger Coulomb interaction, indicating emission from a source of smaller spatial-temporal extent than less energetic pairs. This trend can be understood in the context of a statistical model that allows the source characteristics to evolve as the fragments are emitted.