Fragment multiplicity dependent charge distributions in heavy ion collisions

The dependence of intermediate-mass-fragment (IMF) element distributions on the multiplicity, N{sub IMF}, of detected fragments has been measured for {sup 84}Kr+{sup 197}Au collisions at E/A=35, 55, 70, 100, 200, and 400 MeV. The observed dependence can be parametrized as P(N{sub IMF}{vert_bar}Z){proportional_to}P(Z)exp({minus}c{center_dot}N{sub IMF}{center_dot}Z), where c is a beam-energy and excitation-energy dependent parameter. Previous work indicated this parameter is zero in the liquid-gas coexistence region and positive in the gaseous phase. In contrast, we observe both negative and positive values for c, revealing the meaning of this parameter to be less straightforward than previously assumed. The magnitude of c appears nonetheless to provide a nontrivial test of multifragmentation models. {copyright} {ital 1997} {ital The American Physical Society}