Pairing transition of nuclei at finite temperature

Pairing transition at finite temperature was investigated by the shell model and BCS calculations. The definitive signature of pairing transition is identified by a “transition temperature” Tt estimated from a “thermal” odd-even mass difference, while there is no sharp phase transition because of the finiteness of nucleus. It is found that Tt is in good agreement with predictions of critical temperature Tc in the BCS approximation, and the pairing correlations almost vanish at two points of the transition temperature T ≈ 2Tt. The BCS calculations show that the critical temperature Tc increases with increasing deformation. PACS: 21.60.Cs, 21.10.Ma, 05.30.-d