Observation of oscillations and near-barrier suppression in the fusion of ${}^{20}$O + p

Using an active target detector, the fusion excitation function for ${}^{20}$O + ${}^1$H was measured for the first time. Near the barrier, the fusion cross section manifests an oscillatory behavior with broad peaks $\sim$50-100 keV wide. The presence of these peaks likely reflects the low density of low-angular-momentum states in the quasibound regime. R-matrix coupled channel (CC) calculations that include the first excited 2${}^{+}$ state in ${}^{20}$O are able to reproduce the observed oscillations. However, one channel CC calculations fail to reproduce the decrease in the sub-barrier cross section experimentally observed.