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Mass and energy distributions of fission-like fragments obtained in the reactions 26Mg+248Cm, 36S+238U and 58Fe+208Pb leading to the formation of 266,274Hs are reported. From the analysis of TKE distributions for symmetric fragment it was found that at energies below the Coulomb barrier the bimodal fission of 274Hs, formed in the reaction 26Mg+248Cm, is observed, while in the reaction 36S+238U at these energies the main part of the symmetric fragments arises from the quasi-fission process. At energies above the Coulomb barrier the fusion-fission is a main process leading to the formation of symmetric fragment for the both reactions. In the case of 58Fe+208Pb reaction the quasi-fission process is the main reaction mechanism at all measured energies. The pre- and post-scission neutron multiplicities as a function of the fragment mass have been obtained for all studied reactions. [ABSTRACT FROM AUTHOR]

Average preequilibrium npreeq> average statistical prescission nstpre> and postscission npost> neutron multiplicities as well as average γ-ray multiplicity , average energy emitted by γ-rays and average energy per one gamma quantum <[variant_greek_epsilon]γ> as a function of mass and total kinetic energy (TKE) of fission fragments were measured in the proton-induced reactions p+232Th→233Pa, p+238U→239Np and p+242Pu→243Am (at proton energy Ep=13, 20, 40 and 55 MeV). The fragment mass and energy distributions (MEDs) have been analyzed in terms of the multimodal fission. The decomposition of the experimental MEDs onto the MEDs of the distinct modes has been fulfilled in the framework of a method that is free from any parameterization of the distinct fission mode mass distribution shapes. The main characteristics for symmetric and asymmetric modes have been studied in their dependence on the compound nucleus composition and proton energy. The manifestation of multimodal fission in average γ-ray multiplicities of fission fragments was also studied in this work. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Data have been obtained on exclusive single neutron knockout cross sections from 12Be to study its ground state structure. The cross sections for the production of 11Be in its ground state (1/2+) and first excited state (0.32 MeV, 1/2-) have previously been measured, indicating a strong (2s1/2)2 component to the 12Be ground state. In the present experiment, performed at the GANIL laboratory, cross sections for the first (0.32 MeV, 1/2-) and second (1.78 MeV, 5/2+, unbound) excited states in 11Be were measured, which gives information on the admixture of (1p1/2)2 and (1d5/2)2 components in the ground state of 12Be. A fragmentation beam of 12Be of ∼10000 pps (95% pure) was incident on a carbon target at 41 MeV/u. The beam particles were tracked onto the target, and their energies were measured event-by-event. The beam-like residues were measured in a position sensitive telescope mounted at zero degrees, and neutrons were measured in the DéMoN array. The 1/2- state of 11Be was identified by measuring coincident 320 keV γ-rays, using four NaI detectors. Full kinematic reconstruction of unbound states in 11Be was performed using coincident neutrons and 10Be ions. Detailed simulations were performed in order to interpret the data, and spectroscopic factors were calculated, using preliminary single particle removal cross sections calculated using a Glauber model. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The fusion-fission process for the synthesis of superheavy elements is discussed on the basis of the fluctuation-dissipation model. Recently the experiments at Dubna on fission of superheavy nuclei were carried out, and the mass and total kinetic energy distributions of fission fragments were measured. By analyzing the mass distribution of fission fragments, we can distinguish between fusion-fission process and quasi-fission process. We employ three-dimensional Langevin equation. We find almost all of the mass symmetric fission events come from the quasi-fission process in the superheavy mass region. In order to classify the fusion-fission paths and compare with the experimental data directly, we analyze the pre-scission neutron emission in the correlation with fission fragments. The neutron multiplicity depends on the travelling time of the trajectory. It is useful to investigate the fusion-fission process. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]