The fusion-fission and quasi-fission processes in the reaction 48Ca+208Pb at energies near the Coulomb barrier

Mass-energy distributions (MEDs) and capture-fission cross sections have been measured in the reaction Ca-48 + Pb-208 -> No-256 at the energies E-lab = 206-242 MeV using a double-arm time-of-flight spectrometer CORSET. It has been observed that MED of the fragments consists of two parts, namely, the classical fusion-fission process corresponding to the symmetric fission of 256No and quasi-fission shoulders corresponding to the light fragment masses similar to 60-90 u and complimentary heavy fragment masses. The quasi-fission shoulders have a higher total kinetic energy (TKE) as compared with that expected for the classical fission. A mathematical formalism was employed for the MEDs fragment decomposition into fusion-fission and quasi-fission components. In the fusion-fission process a high-energy Super-Short mode has been discovered for the masses M-H = 130-135 u and the TKE of approximate to 233 MeV. (C) 2008 Elsevier B.V. All rights reserved.