Disentangling reaction mechanisms forαproduction in the6Li +209Bi reaction

Abstract

Inclusive breakup $\ensuremath{\alpha}$ cross sections (${\ensuremath{\sigma}}_{\ensuremath{\alpha}}^{\mathrm{incl}}$) are measured for the ${}^{6}$Li + ${}^{209}$Bi reaction at bombarding energies ${E}_{\mathrm{lab}}=24$--50 MeV. The ${\ensuremath{\sigma}}_{\ensuremath{\alpha}}^{\mathrm{incl}}$ was observed to be a substantial fraction of the total reaction cross section over the entire energy range, and it exhausts almost whole of the reaction cross section at sub-barrier energies. An investigation on the origin of large inclusive $\ensuremath{\alpha}$ reveals that most of the $\ensuremath{\alpha}$ particles are produced by noncapture breakup (${}^{6}$Li$\phantom{\rule{0.16em}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha}+d$) and incomplete fusion via $d$ capture. The combined cross sections of noncapture breakup, $d$ capture, and transfer reactions successfully explain the origin of most of the experimental ${\ensuremath{\sigma}}_{\ensuremath{\alpha}}^{\mathrm{incl}}$ over the measured energy range. A comparison of the ${\ensuremath{\sigma}}_{\ensuremath{\alpha}}^{\mathrm{incl}}$ versus reduced energies for several targets involving ${}^{6}$Li as projectile shows that the cross sections are independent of target. Interestingly, the difference between reaction and complete fusion cross sections ``${\ensuremath{\sigma}}_{\mathrm{reac}}\ensuremath{-}{\ensuremath{\sigma}}_{\mathit{CF}}$'' for several reactions also shows the same behavior.