Evidence For Superdeformed Shape Isomeric States In Si-28 At Excitations Above 40 Mev Through Observations Of Selective Particle Decays Of O-16+C-12 Resonances In Be-8 And Alpha-Channels

Excitation functions of the reactions C-12(O-16 Be-8)Ne-20 and C-12(O-16, He-4)Mg-24 leading to several states have been measured in the range E(c.m.) = 25.7-38.6 MeV. From cross channel correlation analysis two intermediate resonance structures at E(c.m.) = 26.9 and 29.5 MeV corresponding to excitation energies of 43.7 and 46.2 MeV in Si-28 have been identified. Angular distribution measurements for C-12(O-16,He-4)Mg-24(g.s.) have also been made at the lower resonance at E(c.m.) = 26.9 MeV which enable spin assignment of J(pi) = 14+ to this resonance. Striking observation of preferential Be-8 decay of both the resonances to the 8-particle-4-hole states in Ne-20 is interpreted as evidence for the resonances to be highly deformed shape isomeric configurations in Si-28 expected from deformed shell-model calculations.