Strong evidence for quasifission in asymmetric reactions formingPo202

Abstract

Fission fragment mass-angle correlations and mass ratio distributions have been measured for the reactions 16 O + 186 Os, 24 Mg + 178 Hf, 34 S + 168 Er, and 48 Ti + 154 Sm, forming the 202 Po composite nucleus, at near barrier energies. Systematic analysis based on the expected dependence of the variance of the mass distribution on the angular momentum and temperature of the compound nucleus indicate that the two lighter systems evolve through true compound nucleus fission. Evidence of quasifission was observed for the two most mass-symmetric reactions, through strong mass-angle correlations for the 48 Ti + 154 Sm reaction and a broadened mass ratio distribution for the 34 S + 168 Er reaction. Furthermore, the increase in mass width at near barrier energies shows the influence of the alignment of statically deformed target nuclei.

Recent results of measurements of evaporation residue excitation functions for19F+194,196,198Pt and16,18O+198Pt systems with HYRA spectrometer at IUAC

“…The data shows that ER cross section increases with increasing values of N/Z of the compound nuclei in an isotopic chain. Similar observation was made earlier for other systems [18,19]. The survival probabilities of the compound nuclei 214 Rn and 216 Rn formed in the 16,18 O+ 198 Pt reactions are next shown in Figure 5 (b).…”

“…3 The case for 19 We next perform statistical model calculations for the interpretation of the ER data. The detail of the calculations can be found in Ref.…”

Fusion – fission dynamics: fragment mass distribution studies

“…Therefore, if the proportion of the quasi-fission reaction increases with change in the excitation energy, there will be an increase in the width of the mass distribution deviating from the trend. Such an increase in the width of fragment mass distribution with the decrease in energy has been reported recently around the Coulomb barrier [18,19]. Similar anomalous increase in the width of mass distribution was observed with decrease in beam energy in fusion of systems with the deformed 232 Th target [20].…”

“…00004-p.4 Masses of fission fragments were extracted from the time of flight differences of the fission fragments [18]. The method is particularly useful, when the beam resolution is not good (particularly for cyclotron).…”

Fusion and quasi-fission in the formation of heavy elements

“…The experimental methods and analysis procedures are described in Refs. [13,14]. Examples for a fusion-fission reaction (left panel of Fig.…”