Nuclear temperature of the disassembling source in central heavy-ion collisions from isotope yields

We modify the method of Albergo {ital et} {ital al}. for determining the temperature of an excited nucleus from double ratios of isotope yields and present a statistical model which accounts for the population and decay of excited states of the emitted fragments. Nuclear temperatures are extracted using experimental ratios of isotopic yields of fragments from helium through carbon for the reactions {sup 40}Ca + {sup 58}Ni, {sup 40}Ar + {sup 58}Ni, {sup 40}Ca + {sup 58}Fe, and {sup 40}Ar + {sup 58}Fe at 33 MeV/nucleon projectile energy. Using the model we obtain consistent values for the temperature from various isotope combinations within the experimental error when accounting for the population and decay of the excited fragments. {copyright} {ital 1996 The American Physical Society.}