Comparative analysis of the energy dependences of the induced fission times for the Pb-like and U-like nuclei obtained by the crystal blocking technique

Comparative analysis of the experimental data on the induced fission lifetimes for the Pb-like and U-like nuclei produced in the 208Pb + 28Si and 238U + 28Si reactions obtained by the crystal blocking technique was performed, within the dynamical approach based on Langevin equations taking into account light particle emission from the hot fissioning system. A discussion of the energy dependence of the time values for U-like nuclei allows to obtain information on the magnitude of nuclear viscosity

Dynamical analysis of the induced fission time obtained by the crystal blocking technique for the 235U + α reaction

The crystal blocking technique has been used to measure the total time of the induced fission process for the 235U + α reaction in the energy rage of bombarding α-particles from 25.9 to 31.2 MeV. The experimental fission lifetimes observed in this reaction vary from 10-17 to 10-16 s, depending on the projectile energy. The experimental data (along with the corresponding data on the angular anisotropy and fissionability of Pu isotopes produced in the investigated reaction) have been analyzed within the dynamic-statistical approach with allowance for the nuclear dissipation phenomenon and the double-humped fission barrier model. It is demonstrated that the time of induced fission reaction at low excitation energies is sensitive to the nuclear viscosity

Pre-equilibrium α-particle emission as a probe to study α-clustering in nuclei

A theoretical approach was developed to describe secondary particle emission in heavy ion collisions, with special regards to pre-equilibrium α-particle production. The probabilities of neutron, proton and α-particle emission have been evaluated for both the equilibrium and pre-equilibrium stages of the process. Effects due the possible cluster structure of the projectile which has been excited during the collisions have been experimentally evidenced studying the double differential cross sections of p and α-particles emitted in the E=250MeV 16O +116Sn reaction. Calculations within the present model with different clusterization probabilities have been compared to the experimental data