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 48Ca + 208Pb → 256No at the energies Elab=206–242MeV 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 ∼60–90u 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 MH=130–135u and the TKE of ≈233MeV.