Competition of fusion and quasifission in reactions leading to production of superheavy elements

The mechanism of fusion hindrance, an effect observed in the reactions of cold, warm, and hot fusion leading to production of superheavy elements, is investigated. A systematics of transfermium production cross sections is used to determine fusion probabilities. The mechanism of fusion hindrance is described as a competition of fusion and quasifission. Available evaporation residue cross sections in the superheavy region are reproduced satisfactorily. Analysis of the measured capture cross sections is performed and a sudden disappearance of the capture cross sections is observed at low fusion probabilities. A dependence of the fusion hindrance on the asymmetry of the projectile-target system is investigated using the available data. The most promising pathways for further experiments are suggested. (C) 2003 MAIK "Nauka/Interperiodica".