α-Emission temperatures, coulomb instabilities and nuclear cracking

Abstract The α-emission temperatures of medium mass nuclei with masses near 140, determined at excitation energies from 2 to 4.3 MeV/nucleon, suggest a rapid increase in the heat capacity of the composite system consistent with model predictions of the onset of a cracking phase transition or fragmentation. The limiting value of the temperature, near 6 MeV, provides evidence for a soft nuclear equation of state ( K ⋍ 220 MeV ) at these high excitation energies.