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Pre-scission neutron multiplicities have been measured for 12C + 194, 198Pt systems at matching excitation energies at near Coulomb barrier region. Statistical model analysis with a modified fission barrier and level density prescription have been carried out to fit the measured pre-scission neutron multiplicities and the available evaporation residue and fission cross sections simultaneously to constrain statistical model parameters. Simultaneous fitting of the pre-scission neutron multiplicities and cross section data requires shell correction at the saddle point.

Fission fragment angular distributions have been measured for 16O + 194Pt reaction forming the compound system 210Rn, in the laboratory energy range from 79 to 90 MeV. The measured fission fragment anisotropies as a function of E c . m . / V B are compared with the predictions of standard saddle point statistical model ( sspm ). Anisotropies calculated using the average excitation energy and angular momentum values could not reasonably fit the experimental data. Statistical model calculations were performed using the pace with modified fission barrier and level density parameters. Fission probability, evaporation residue cross section and neutron multiplicity were simultaneously used to fix the statistical parameters. Model calculations incorporating the chance nature of fission decay and scaled values of the rotating finite range model (RFRM) moment of inertia could reasonably fit the fragment angular anisotropies.

We present γ-ray multiplicity distributions for the formation of evaporation residues in the fusion reaction 19F + 184W → 20383Bi120 at beam energies in the range of 90–110 MeV. The measurements were carried out using a 14 element BGO detector array and the Heavy Ion Reaction Analyzer at the Inter University Accelerator Centre. The data have been unfolded to obtain angular momentum distributions with inputs from the statistical model calculation. Comparison with another neighboring system, viz. 19F + 175Lu → 19480Hg114 with nearly similar entrance-channel mass asymmetry, hints at the depletion of higher angular momenta after crossing of the Z=82 shell in the compound nucleus.

Fission fragment mass angle correlation and mass ratio distributions have been measured for 16 O + 194 Pt reaction forming the composite system 210 Rn in the energy range 75 MeV to 102 MeV in laboratory frame. No mass angle correlation was observed and the mass ratio distributions were compared with theoretical calculations assuming compound nucleus formation. No evidence of quasi-fission process is observed in the reaction.

In order to study complete and incomplete fusion in heavy ion reactions, the excitation functions for several residues produced in the system 16O + 159Tb have been measured in the energy range ≈ 70 – 95 MeV , employing activation technique. The measured excitation functions have been compared with those calculated using computer codes CASCADE, PACE2 and ALICE-91. Comparison of measured and theoretically calculated excitation functions has indicated significant contributions from incomplete fusion in some α-emission channels. In the present experiment, the recoil range distributions of several residues at ≈ 90 MeV incident beam energy have also been measured using recoil catcher technique and off-line gamma ray spectrometry. Analysis of the recoil range distributions has further confirmed the presence of contributions from incomplete fusion reactions. An attempt has been made to separate out the relative contributions of complete and incomplete fusion channels.