-decay of excited states in C and B

Studies of the 16O(9Be, α7Be)14C and 7Li(9Be, α7Li)5He reactions at Ebeam=70MeV have been performed using resonant particle spectroscopy techniques. The 11C excited states decaying into α+Be7(gs) are observed at 8.65, 9.85, 10.7 and 12.1 MeV as well as possible states at 12.6 and 13.4 MeV. This result is the first observation of α-decay for excited states above 9 MeV. The α+Li7(gs) decay of 11B excited states at 9.2, 10.3, 10.55, 11.2, (11.4), 11.8, 12.5, (13.0), 13.1, (14.0), 14.35, (17.4) and (18.6) MeV is observed. The decay processes are used to indicate the possible three-centre 2α+He3(H3) cluster structure of observed states. Two rotational bands corresponding to very deformed structures are suggested for the positive-parity states. Excitations of some observed T=1/2 resonances coincide with the energies of T=3/2 states which are the isobaric analogs of the lowest 11Be states. Some of these states may have mixed isospin.