We investigate the liquid-gas phase transition of dense matter in supernova explosion by the relativistic mean field approach and fragment based statistical model .
The boiling temperature is found to be high ( T _ { boil } \geq 0.7 \mbox { MeV } for \rho _ { \scriptscriptstyle B } \geq 10 ^ { -7 } \hbox { fm } ^ { -3 } ) , and adiabatic paths are shown to go across the boundary of coexisting region even with high entropy .
This suggests that materials experienced phase transition can be ejected to outside .
We calculated fragment mass and isotope distribution around the boiling point .
We found that heavy elements at the iron , the first , second , and third peaks of r-process are abundantly formed at \rho _ { \scriptscriptstyle B } = 10 ^ { -7 } , 10 ^ { -5 } , 10 ^ { -3 } and 10 ^ { -2 } \hbox { fm } ^ { -3 } , respectively .