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In the reactions with heavy ions leading to superheavy nuclei the formation of a compound nucleus is suppressed strongly by competing quasifission process and deep inelastic collisions. Moreover, the excited compound nucleus formed in fusion reactions mainly undergoes fission. The study of fission of heavy and superheavy nuclei gives important information about compound nucleus formation cross sections, fission barriers and survival probabilities of these nuclei. The main recent results of the experimental studies of the compound nucleus fission and quasifission processes in the heavy-ion-induced reactions leading to the formation of nuclei with Z ≥ 102 are discussed. The most attention is paid to the experimental investigations of mass-energy distributions of reaction products measured using the CORSET spectrometer. [ABSTRACT FROM AUTHOR]

We have studied the dependence of the production cross-sections of the isotopes 282, 283112 and 286-288114 on the excitation energy of the compound nuclei 286112 and 290114. The maximum cross-sections of the xn-evaporation channels for the reaction 238 U(48 Ca, xn)286-x112 were measured to be: σ3n = 2.5+1.8-1.1pb and σ4n = 0.6+1.6-0.5pb; for the reaction 242 Pu(48 Ca, xn)290-x114: σ2n ∼ 0.5pb, σ3n = 3.6+3.4-1.7pb and σ4n = 4.5+3.6-1.9pb. In the reaction 233 U(48 Ca, 2-4 n)277-279112 we measured an upper cross-section limit of σxn≤0.6pb. An increase of σER in the reactions of actinide targets with 48Ca can be due to the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N = 184. The observed nuclear decay properties of the nuclides with Z = 104-118 are compared with theoretical nuclear mass calculations and the systematic trends of α-decay properties. As a whole, they give a consistent pattern of decay of the 18 even- Z neutron-rich nuclides with Z = 104-118 and N = 163-177. [ABSTRACT FROM AUTHOR]

Recent experimental data on relatively mass-asymmetric collisions show that fusion hindrance can be explained in terms of the onset of quasi-fission reactions. The influence of mass-asymmetry, shell effects and target deformation on such phenomena is presented and possible implications for super-heavy element production are discussed. [ABSTRACT FROM AUTHOR]

The upgraded separator VASSILISSA was used to confirm results of previous experiments on the synthesis of the heavy isotopes of the element 112 obtained in complete-fusion reactions of 48Ca and 238U. An additional reason was the non-observation of any events in the same reaction studied with the BGS separator at Berkeley. Limits of 280 < A < 286 for the atomic mass number of the observed spontaneously fissioning isotope were measured. The obtained results on the decay mode, half-life and production cross-section are in agreement with those obtained in our first experiment. [ABSTRACT FROM AUTHOR]

To study basic properties of the fusion reaction dynamics for heavy compound systems the partial-wave distribution σell can be employed as an alternative to the classically used fusion/fission excitation functions. A variety of reactions leading to compound nuclei (CN) in the Pb region can be used to investigate features like the fusion-fission competition, the role of deformation in the fusion of heavy systems and a possible effect of the Z 82 shell on the enhancement of evaporation residue (ER) production. [ABSTRACT FROM AUTHOR]