INFLUENCE OF PARTICLE-NUMBER PROJECTION ON POTENTIAL-ENERGY SURFACES OF FISSIONING NUCLEI

The deformation dependence of the particle number uncertainty (inheren t to almost all fission calculations due to the BCS formalism) is anal yzed. The use of particle number projection after BCS variation (PBCS) and before variation (FBCS) indicates noticeable fluctuations of the BCS pairing energy over the whole the Potential Energy Surface (PES). For significant deformation points of the Pu-240(94) pES energy fluctu ations obtained by the PBCS method up to 0.9 MeV are observed. The ene rgy fluctuations due to the FBCS method show smoother behaviour but ar e essential at deformation points where a decreasing level density at the vicinity of the Fermi level (decreasing pairing correlations) occu rs. At such points the FBCS method yields nontrivial solutions compare d to the trivial one given by the standard BCS theory. The smallest ne utron number uncertainty is obtained in the vicinity of the isomer min imum due to a pronounced shell structure there. The case of surface de pendent BCS parameters is also studied. The results indicate that FBCS should be used whenever possible.