Measurements of evaporation residue cross sections and spin distributions for 240 Cf and 186 Pt compound nuclei

Abstract

The present thesis work deals with the study of the dynamics of heavy- ion-induced nuclear reactions. The evaporation residue (ER) cross- sections in the heavy mass region can be interpreted as a signature of the survival of the compound nucleus (CN) against fission. ER cross- section measurements and ER-gated spin distributions were carried out for the 32S+154Sm and#8594; 186Pt system and measurements of ER cross- section only for the 32S+208Pb and#8594; 240Cf system at the Pelletron-LINAC facility at Inter University Accelerator Center (IUAC), New Delhi. The Hybrid Recoil Mass Analyzer (HYRA) in conjunction with the TIFR 4and#960; (Tata Institute of Fundamental Research) spin-spectrometer was used to measure the ER cross-section and spin distributions. In addition to the ER cross-section, the multiplicity and spin distribution of 186Pt system were extracted from the experimentally measured ER-gated fold data. The response matrix generated using GEANT4 simulations of TIFR 4and#960; spin spectrometer was used to obtain the spin distributions. The theoretical analysis of the 186Pt data was carried out using both a modified statistical model and advanced dynamical model calculations. The statistical model calculations provided considerable information about the role of fission barrier heights and nuclear viscosity in the formation of the ERs. The dynamical model calculations demonstrated the contribution of incomplete fusion for ER production. The primary outcome of this model calculation is the demonstration of the role of incomplete fusion to reproduce the ER cross-sections. newlineThe second system 240Cf compound nucleus is among the heaviest systems to be studied in the country for measuring the ER cross- section. This system is highly fissile and has an extremely low fission barrier. Theoretical calculations for this system are currently underway to complement the measurement of ER and improve our understanding of the dynamics taking place in the pre-saddle region. newline newline