Influence of a one-neutron-excess projectile on low-energy incomplete fusion

Abstract

Background: Incomplete fusion has been found to be an important contributor in light heavy-ion ($A\ensuremath{\le}20$) induced reactions even at slightly above barrier energies.Purpose: For better insight into the dynamics of incomplete fusion, the onset and influence of incomplete fusion need to be investigated in terms of projectile energy (${E}_{\mathrm{lab}}$) and entrance channel mass-asymmetry (${\ensuremath{\mu}}_{A}$). A rich set of experimental data on incomplete fusion may be useful to correlate the probability of incomplete fusion with the various entrance channel parameters and eventually to develop a theoretical model code for the same. Presently, there is no theoretical model available which can explain low-energy incomplete fusion data consistently.Methods: The excitation functions of complete and incomplete fusion residues populated in the $^{13}C$+$^{169}\mathrm{Tm}$ system have been measured using the recoil-catcher activation technique followed by offline $\ensuremath{\gamma}$ spectroscopy. The evaporation residues have been identified on the basis of characteristic $\ensuremath{\gamma}$ lines and confirmed through the decay-curve analysis.Results: The excitation functions of $xn$ and $pxn$ channels are found to be in good agreement with the statistical model code pace4; this suggests the population of these channels via complete fusion. Some residues are found to have a contribution from their higher charge isobar precursor decay. The precursor contribution has been deduced from the cumulative cross section using the standard successive radioactive decay formulations. The excitation functions of $\ensuremath{\alpha}$-emitting channels are observed to be significantly enhanced as compared to the statistical model code pace4. This enhancement may be attributed to the contribution from incomplete fusion. The incomplete fusion strength function for $^{13}C$+$^{169}\mathrm{Tm}$ is compared with that obtained in the $^{12}C$+$^{169}\mathrm{Tm}$ system. It has been found that the one-neutron (1$n$) excess projectile $^{13}C$ (as compared to $^{12}C$) results in a less incomplete fusion contribution due to its relatively large negative alpha-$Q$ value. Recently proposed ``alpha-$Q$-value systematics'' seems to explain incomplete fusion data.