Enhanced Monopole Transition Strength From The Cluster Decay Of C-13

The inelastic excitations and cluster decay of C-13 have been measured using the reaction, Be-9(C-13,C-13* -> Be-9 + alpha)Be-9. We observe strong excitation to the 14.3-MeV (1/2(-)) resonant state from the cluster-decay channel, leading to an enhanced monopole matrix element of (6.3 +/- 0.6) fm(2). This large cluster-related monopole strength is a clear indication of the cluster-structure domination of this state and is consistent with the recent prediction of the orthogonality condition model (OCM). It would be interesting to further explore the three-center molecular rotational band that is initiated from the observed band-head.