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Evaporation residue cross sections and spin distributions have been measured for 200 Pb compound nucleus formed in 16 O+ 184 W reaction at the laboratory beam energies of 84, 92, 100, 108, 116, and 120 MeV. The evaporation residues have been selected using the recoil mass spectrometer, HIRA and detected using a 2D position sensitive silicon detector. The evaporation residue spin distributions have been measured by detecting gamma rays with 14 element BGO multiplicity filter. Measured evaporation residue cross sections and spin distributions are compared with the values predicted by a standard statistical model code. Comparison shows that, in the energy region studied, the nuclear viscosity parameter γ = 3 is required to explain total evaporation residue cross sections and evaporation residue spin distributions.

Evaporation residue cross sections for the reaction 16 O + 194 Pt were measured at beam energies in the range 75.4-103.1 MeV using the gas-filled separator Hybrid Recoil Mass Analyzer at the Inter University Accelerator Centre, New Delhi. The transmission efficiency of the separator was obtained using the calibration system 16 O + 184 W and a Monte Carlo simulation code. Measured evaporation residue cross sections were fitted with statistical model calculations using Kramers' formula. The present measurement provides further evidence for the onset of dissipative forces in fission in the mass ∼200 region.