Effects of entrance channels on breakup fusion induced by F19 projectiles

Abstract

The study of breakup fusion of $^{19}\mathrm{F}$ with $^{154}\mathrm{Sm}$ target was studied through offline $\ensuremath{\gamma}$ ray spectrometry. Partial cross sections of evaporation residues produced in this reaction were measured in center-of-mass energies ranging $\ensuremath{\approx}3--30$ MeV above the fusion barrier. The excitation functions of the evaporation residues populated through $xn/pxn$ channels were found to be satisfactorily reproduced by statistical model calculations, whereas for the $\ensuremath{\alpha}$ emitting channels the cross sections show an enhancement over the theoretical predictions. The critical angular momentum deduced from the measured cross sections was found to be in good agreement with statistical model calculations. The degree of fusion incompleteness in the $^{19}\mathrm{F}+^{154}\mathrm{Sm}$ reaction is estimated by comparing the fusion excitation functions with coupled channels calculations and the extracted fusion function with the universal fusion function. The large cross sections observed for incomplete fusion products support the interpretation that this suppression of fusion is caused by $^{19}\mathrm{F}$ breaking up into charged fragments before reaching the fusion barrier. The incomplete fusion probability was also found to increase with the reduced mass and charge of the entrance channel, indicating the influence of entrance channel mass asymmetry and Coulomb repulsion on incomplete fusion. The present analysis shows the presence of strong clustering in the $^{19}\mathrm{F}$ projectile as $\ensuremath{\alpha}$ and $^{15}\mathrm{N}$.