Limiting temperatures of neutron rich nuclei: A possible interpretation of data from isotope yield ratios

Abstract

The recent ALADIN report of limiting temperatures for nuclear disassembly, derived from measurements of isotopic ratios for He and Li nuclei, is discussed. It is suggested that the entire excitation energy dependence which is observed may result from the fact that limiting temperatures for the onset of Coulomb instability are being measured for progressively lighter neutron rich nuclei as the excitation energy per nucleon increases. While the basic observation of plateauing in the intermediate excitation energy range remains valid, the higher excitation results may not signal entry into the vapor phase. The ALADIN result for A\ensuremath{\approxeq}125, when combined with lower energy data, indicates a plateau temperature near 6.5 MeV over the range of 3--11 MeV/nucleon initial excitation energy.