Instability of hot nuclei

A hot nucleus is unstable if its temperature exceeds a certain limiting value due to the Coulomb repulsion between its protons. This instability is investigated using a finite-temperature generalization of the liquid-drop model. For this purpose an equation of state for asymmetric nuclear matter derived in a previous work with the use of a Skyrme-type effective interaction is generalized to the case of a density-dependent effective mass. Standard parametrizations of the Skyrme interaction are used to study the properties of a hot ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ nucleus immersed in a uniform vapor. Good agreement is achieved between the present model and the results of finite-temperature Hartree-Fock calculations only if the Coulomb interaction between the vapor and the drop is properly taken into account. The results are seen to yield valuable information on the temperature dependence of the surface tension of hot nuclei.