Spinodal vaporization – a critical and imposing decay mode of highly excited nuclear systems

Abstract

A novel prompt decay mode of highly excited nuclear systems is shown to set in with necessity as a certain critical excitation energy per nucleon is reached. It is driven by a peculiar, open-ended type of spinodal instability, unique to self-bound open systems, and consists in parts of the system undergoing spontaneous indefinite thermal expansion ending in vaporization into the surrounding open space. The mode, named here spinodal vaporization, is distinctly different from all known decay modes of excited nuclei and faces no competition from the latter. It sets a natural upper limit for the excitation energy that can be thermalized by compound nuclear systems, while setting also a limit to the applicability of thermodynamics to the description of highly excited nuclear systems.