Direct Evidence for a Narrow Window at High Angular Momentum in Incomplete-Fusion Reactions

Alpha-gamma coincidence measurements have been made with reactions of 142-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ on ${}_{}{}^{146}{}_{}{}^{}\mathrm{Nd}$ leading to the noncollective nuclei ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Dy}$. The side-feeding pattern in coincidence with forward energetic alpha particles peaks at $J=30\mathrm{}$ with full width at half maximum ∼10, indicating that central collisions do not participate, while that for backward alpha particles extends down to $J=0\mathrm{}$. The data are consistent with the generalized critical-angular-momentum model of incomplete fusion.