Crossing barriers to reach the Super Heavy Elements Island
David Boilley
GANIL
日時：2007年08月06日（月） 16:15-
場所：大学院講義室（総合研究棟7階745号室）
Many models are attempting to describe the fusion process that should lead to the synthesis of super-heavy elements(SHE) in order to help the experimental quest. But there are still too many uncertainties on some key parameters todo reliable predictions. The few evaporation cross sections available are not enough to validate the models and onehas to find other means. In this seminar, I will present some criteria that should help to characterize the barriersthat should be or not be crossed to form a SHE.Some experiments were performed at GANIL to try to locate the island of stability of the SHE by measuring thefission time. Based on the crystal blocking technique, they have shown some direct evidences for very long fissiontimes of the SHE. Is this observation due to a high fission barrier or to other mechanisms?I will present some fission-time calculation made with KEWPIE2, which is a new dynamical cascade code devoted to theSHE. It has been first compared to the evaporation cross section obtained by cold and hot fusion in order to fix theonly two free parameters. The calculated fission time distribution will be analyzed and compared to the experimentalresults in order to get some constraints on the fission barrier.The saddle-to-scission time cannot be neglected for these nuclei. For that purpose, we derived a new formula thatcan accommodate any kind of potential. I will show some preliminary results on the influence of isomeric potentialpockets.As for the fusion part, the fusion hindrance that is commonly explained by the existence of a second barrier on theway to the ground state gives some constraints on the neck parameter. I will show our latest results on the subject.