| Vol. 53,
No. 3 September 1999 pp.409-418 Fusion-fission dynamics in the superheavy nucleus production G GIARDINA 1 , P D'AGOSTINO 1 ,G FAZIO 1 , M HERMAN 2 , A I MUNINOV 3 , A NASIROV 3;4 ,G OLIVA 1 ,R PALAMARA 5 and R RUGGERI 1 1 Istituto
Nazionale di Fisica Nucleare, Sezione di Catania,
Dipartimento di Fisica dell'Universit` a di Messina,
98166 Messina, Italy Abstract. The fusion-fission reaction mechanism leading to the massive nucleus formation is studied. We investigate the superheavy nucleus formation in heavy-ion induced reactions by analysing the evaporation residue (ER) production in order to study the fusion dynamics and the decay proper-ties of nuclei close to the stability island at Z = 114. We consider the 64 Ni + 208 Pb, 48 Ca + 238 U and 48 Ca + 244 Pu reactions that lead to the Z = 110; 112 and 114 superheavy elements respectively. By using the dinuclear system (DNS) concept of the two interacting nuclei we calculate the quasifission-fusion competition in the entrance channel and the fission-evaporation competition along the de-excitation cascade of the compound nucleus. The dynamics of the entrance channel allows us to determine the beam energy window which is favorable to the fusion, while the dynamic evolution of the compound nucleus on the shell correction to the fission barrier and the dissipative effects influence the fission-evaporation competition in order to obtain the residue nuclei from the superheavy nucleus formation. We also calculate the G n / G tot ratio at each step of the de-excitation cascade of the compound nucleus and we present a systematics of G n / G tot (at first step of the cascade) for many reactions that lead to nuclei with Z = 102-114. Keywords. Quasifission; fusion; fission; evaporation residues; superheavy elements. PACS Nos 25.70.-z; 25.70.Jj; 27.90.+b |