Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in ${}^4\mathrm{He}$, ${}^5\mathrm{Li}$, and ${}^8\mathrm{Be}$, were determined for spectator fragmentation, following collisions of ${}^{197}\mathrm{Au}$ with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.

• Received 30 August 2007

DOI:https://doi.org/10.1103/PhysRevC.76.064606