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" T-t 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 T-t is in good agreement with predictions of critical temperature T-c in the BCS approximation, and the pairing correlations almost vanish at two points of the transition temperature T approximate to 2T(t). The BCS calculations show that the critical temperature T, increases with increasing deformation. (C) 2004 Elsevier B.V. All rights reserved.