Enhanced monopole transition strength from the cluster decay of 13 C

The inelastic excitations and cluster decay of 13C have been measured using the reaction, 9Be(13C,13C* → 9Be + α)9Be. 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) fm2. 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.