Thermal phase transition in nuclear multifragmentation: The role of Coulomb energy and finite size

A systematic analysis of the moments of the fragment size distribution has been carried out for the multifragmentation of $1A\mathrm{GeV}$ Au, La, and Kr on carbon. The breakup of Au and La is consistent with a continuous thermal phase transition. The data indicate that the excitation energy per nucleon and isotopic temperature at the critical point decrease with increasing system size. This trend is attributed primarily to the increasing Coulomb energy with finite size effects playing a smaller role.