Probing the Nuclear Liquid-Gas Phase Transition

TLDR

Fragment distributions from 600 MeV per nucleon Au+Au collisions are investigated. The mass and excitation energy of prefragments were extracted from fragment and neutron distributions, and a temperature scale was obtained from He and Li isotope yield ratios. The isotope temperature–excitation energy relation exhibits phase‑transition behavior, with the nuclear vapor regime appearing at 10 MeV per nucleon, 5 MeV temperature, and a density of 0.15–0.3 normal nuclear density.

Abstract

Fragment distributions resulting from $\mathrm{Au}+\mathrm{Au}$ collisions at an incident energy of $E/A\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}600\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$ are studied. From the measured fragment and neutron distributions the mass and the excitation energy of the decaying prefragments were determined. A temperature scale was derived from observed yield ratios of He and Li isotopes. The relation between this isotope temperature and the excitation energy of the system exhibits a behavior which is expected for a phase transition. The nuclear vapor regime takes over at an excitation energy of 10 MeV per nucleon, a temperature of 5 MeV, and may be characterized by a density of 0.15--0.3 normal nuclear density.