Above-barrier cross sections of α-active heavy reaction products, as well as fission, were measured for the reactions of 10,11 B with 209 Bi. Detailed analysis showed that the heavy products include components from incomplete fusion as well as complete fusion (CF), but fission originates almost exclusively from CF. Compared with fusion calculations without breakup, the CF cross sections are suppressed by 15% for 10 B and 7% for 11 B. A consistent and systematic variation of the suppression of CF for reactions of the weakly bound nuclei 6,7 Li, 9 Be, 10,11 B on targets of 208 Pb and 209 Bi is found as a function of the breakup threshold energy.

Complete fusion excitation functions for 11,10 B+ 159 Tb have been measured at energies around the respective Coulomb barriers, and the existing complete fusion measurements for 7 Li+ 159 Tb have been extended to higher energies. The measurements show significant reduction of complete fusion cross sections at above-barrier energies for both the reactions, 10 B+ 159 Tb and 7 Li+ 159 Tb, when compared to those for 11 B+ 159 Tb. The comparison shows that the extent of suppression of complete fusion cross sections is correlated with the α-separation energies of the projectiles. Also, the two reactions, 10 B+ 159 Tb and 7 Li+ 159 Tb were found to produce incomplete fusion products at energies near the respective Coulomb barriers, with the α-particle emitting channel being the favoured incomplete fusion process in both the cases.PACS number(s): 24.10. Eq, 25.70.Jj, 25.70.Pj, 25.70.Mn, 27.70.+q

Evaporation residue cross sections have been measured following the fusion of 16O with 204Pb, forming the compound nucleus 220Th. These are compared with existing data for the same compound nucleus formed following fusion reactions with 40Ar, 48Ca, 82Se, and 124Sn projectiles. At energies where the reduced cross sections of xn evaporation residues would be expected to be the same for all reactions, those for the heavier projectiles are typically a factor of 10 smaller than those for 16O. This inhibition is attributed to strong competition of quasifission with fusion at the low angular momenta associated with evaporation residue formation.

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Complete and incomplete fusion cross sections for 6 Li + 159 Tb have been measured at energies around the Coulomb barrier by the γ -ray method. The measurements show that the complete fusion cross sections at above-barrier energies are suppressed by ∼34% compared to coupled-channel calculations. A comparison of the complete fusion cross sections at above-barrier energies with the existing data for 11,10 B + 159 Tb and 7 Li + 159 Tb shows that the extent of suppression is correlated with the α separation energies of the projectiles. It has been argued that the Dy isotopes produced in the reaction 6 Li + 159 Tb at below-barrier energies are primarily due to the d transfer to unbound states of 159 Tb, while both transfer and incomplete fusion processes contribute at above-barrier energies.

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