A liquid-gas phase transition for nuclei

In school, most physicists learned the liquid-drop model of the nucleus. In recent years, several groups have addressed the next question: Is there also an equilibrium nuclear “vapor” such that changing a parameter akin to pressure or temperature can send the nucleus back and forth between the two states of matter? Now, two groups have analyzed data from the Indiana silicon sphere (ISiS) experiment at Brookhaven National Laboratory, in which pions and protons were slammed into gold nuclei to induce so-called nuclear multifragmentation. A group from Michigan State University found strong circumstantial evidence for a liquid-gas phase transition, while a group from Lawrence Berkeley National Laboratory was able to fully map out a liquid-vapor coexistence line, with a critical point, in the nuclear phase diagram. That a finite system like a nucleus, with only about 200 particles, not only shows a robust phase transition but also has discoverable quantities like...