Fragmentation analysis of various compound nuclei formed in the mass region 200 and the associated entrance channel effects

The dynamical cluster-decay model (DCM) is employed to analyse the decay of various compound nuclei (CNs) having mass ACN ≈ 200 such as ¹⁹⁴Hg∗, ¹⁹⁷Tl∗, ²⁰²Pb∗ and ²¹⁰Rn∗, formed in ¹⁶O-induced reactions, at common excitation energy E∗ CN ∼ 45 MeV. Calculations are made for three decay fragment configurations, i.e., spherical, β2 -deformed 'hot-compact' and β2 -deformed 'cold-elongated' to study the effect of deformation and orientation in the decay dynamics. The structure of fragmentation potential and preformation probability of the chosen nuclei get the significantly modified after the inclusion of deformation and orientation effects, besides showing a dependence on the mass of CN. Further, an investigation is carried out to see the effect of entrance channel properties on the decay dynamics. For this, three reactions, such as ¹²C +¹⁸²W, ¹⁶O + ¹⁷⁸Hf and ⁴⁰Ar +¹⁵⁴Sm are considered which form the ¹⁹⁴Hg∗ CN at common E∗ CN ∼ 57 MeV. The barrier characteristics, fragmentation structure, preformation probability, barrier penetrability, evaporation residue and fission cross-sections are calculated to analyse the role of the entrance channel in the subsequent decay dynamics. The calculated neutron evaporation residue and fission cross-sections agree well with the experimental data. The most probable fission fragments are identified for the compound nuclei, and the corresponding experimental validation is called for. Moreover, Bohr's independent hypothesis is tested in view of the survival probability (P_surv) of the chosen reactions. (author)