  Studies of the 16O(9Be,alpha7Be)14C and 7Li(9Be,alpha7Li)5He reactions at
E{beam}=70 MeV have been performed using resonant particle spectroscopy
techniques. The 11C excited states decaying into alpha+7Be(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 alpha-decay for excited states above 9
MeV. The alpha+7Li(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
2alpha+3He(3H) 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.
