Enhanced monopole transition strength from the cluster decay of 13 C

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