The potential energy surface of $^{240}$Pu around scission

Some figures may appear in colour only in the online journalThe potential energy surface of $^{240}$Pu is analyzed in the scission region within an elaborate macroscopic-microscopic approach, using the Lublin-Strasbourg-drop model, an improved Strutinsky shell-correction method and the BCS (Bardeen-Cooper-Schrieffer) treatment of pairing. The modified funny-hills nuclear shape parameterization, used in the present study, is further improved by introducing new collective coordinates $\kappa$ and $\psi$ for the elongation and neckconstriction. These variables are shown to be very well suited for the scission region. Within a limited number of dimensions, the model is able to explain fission modes in the actinide region. More specifically, the present work indicates that the peak of the mass distribution at A ≈ 140 in the low-energy fission of $^{240}$Pu is mainly caused by strong neutron shell corrections