Systematic study of projectile structure effect on fusion barrier distribution

Quasielastic excitation function measurement has been carried out for the ${}^4$He + ${}^{232}$Th system at ${\theta }_{lab}$=160${}^{\circ }$ with respect to the beam direction, to obtain a representation of the fusion barrier distribution. Using the present data along with previously measured barrier distribution results on ${}^{12}$C, ${}^{16}$O, and ${}^{19}$F + ${}^{232}$Th systems a systematic analysis has been carried out to investigate the role of target and/or projectile structures on fusion barrier distribution. It is observed that for ${}^4$He, ${}^{12}$C, and ${}^{16}$O + ${}^{232}$Th, reactions the couplings due to target states only are required in coupled channel fusion calculations to explain the experimental data, whereas for the ${}^{19}$F+ ${}^{232}$Th system along with the coupling of target states, inelastic states of ${}^{19}$F are also required to explain the experimental results on fusion-barrier distribution. The width of the barrier distribution shows interesting transition behavior when plotted with respect to the target-projectile charge product for the above systems.