Effect of Closed Shell Structure on Heavy-Ion Fusion Reactions

Abstract

The effect of the nuclear shell structure on the heavy-ion fusion reaction was investigated for the reaction systems 8 2 Se + 1 3 8 Ba, 8 2 Se + 1 3 4 Ba, 1 6 O + 2 0 4 Pb, 8 6 Kr + 1 3 4 Ba, 8 6 Kr + 1 3 8 Ba and 8 2 Se + n a t . Ce. Evaporation residues for these fusion reactions were measured using a recoil mass separator (JAERI-RMS) near Coulomb barrier region. The measured evaporation residue cross sections for the reactions 8 2 Se + 1 3 8 Ba and 8 6 Kr + 1 3 8 Ba were two orders of magnitude and one order of magnitude larger than those for the reactions 8 2 Se + 1 3 4 Ba and 8 6 Kr + 1 3 4 Ba, respectively, at the excitation energy region of 10 ∼ 30 MeV. The evaporation residue cross sections were compared with those of the other reaction systems that make the same or similar compound nuclei as the present reaction systems. It was found that the evaporation residue cross sections correlate strongly with the sum of the shell energies for both projectile and target nuclei, i.e. the evaporation residue cross sections increase as the sum of the shell energy decreases.