Projectile - Mass asymmetry systematics for low energy incomplete fusion

Abstract

Abstract. In the present work, low energy incomplete fusion (ICF) in which only a part of projectile fuses with target nucleus has been investigated in terms of various entrance channel parameters. The ICF strength function has been extracted from the analysis of experimental excitation functions (EFs) measured for different projectile-target combinations from near-to well above-barrier energies in 12 C, 16 O(from 1.02V b to 1.64V b )+ 169 Tm systems. Experimental EFs have been analysed in the framework statistical model code PACE4 based on the idea of equilibrated compound nucleus decay. It has been found that the value of ICF fraction (F ICF ) increases with incident projectile energy. A substantial fraction of ICF (F ICF ≈7 %) has been accounted even at energy as low as ≈ 7.5% above the barrier (at relative velocity v rel ≈0.027) in 12 C+ 169 Tm system, and F ICF ≈10 % at v rel ≈0.014 in 16 O+ 169 Tm system. The probability of ICF is discussed in light of the Morgenstern's mass-asymmetry systematics. The value of F ICF for 16 O+ 169 Tm systems is found to be 18.3 % higher than that observed for 12 C+ 169 Tm systems. Present results together with the re-analysis of existing data for nearby systems conclusively demonstrate strong competition of ICF with CF even at slightly above barrier energies, and strong projectile dependence that seems to supplement the Morgenstern's systematics.