• spectrometer and the associated BGO array. The most remarquable result is the previously unobserved decay path through 28 Si doorway states of energies around 12 MeV leading to the measurement of new capture crosssections. The feeding of specific, deformed states in 28 Si from the resonances is discussed, as well as the selective feeding of 1 + T=1 states around 11 MeV.
IntroductionThe occurence of α clusters in light nuclei is a well established phenomenon known to occur close to their α-decay thresholds, as described by Horiuchi and Ikeda in the late 1960s [1]. As examples of light cluster nuclei, we shall mention here briefly the 8 Be nucleus, which ground state (g.s.) decays into 2 α particles and the 12 C sub-closed shell nucleus which first excited 0 + state is located at 7.65 MeV, near the 8 Be+α fusion threshold. This state, that has been identified by Hoyle to play a major role in the nucleosynthesis of 12 C, is not described by shellmodel calculations but rather by cluster models. The identification of the cluster band built on this 'Hoyle' state is still a challenging goal for experimentalists. In 16 O a clear alpha cluster band has been identified based on a 0 + excited state at 6.05 MeV, a 2 + state at 6.92 MeV and a 2 + state at 10.36 MeV, with large reduced transition probabilities B(E2)(2 + to 0 + )= 27 W.u. and B(E2)(4 + to 2 + )= 65 W.u. A shell-model description of this very deformed band requires 4p-4h (4 particle-4 hole) excitations to be taken into account. What heavier ions are concerned, in the sd shell, in addition to α clusters, 12 C and 16 O are the elementary bricks for the occurence of cluster structures in 24 Mg( 12 C-12 C) and 28 Si( 12 C-16 O). One of the most striking results obtained in the early studies of heavy-ion collisions is the observation of resonant structures in the reaction cross-sections (elastic, inelastic and