ALPHA-DECAY AND PROTON-DECAY OF THE ISOSCALAR E2 RESONANCE IN O-16 AND CA-40

The large α- over proton-decay ratio of the giant isoscalar quadrupole resonance in 16O at Ex≈ 21 MeV (Γrms ≈ 6 MeV) after excitation by inelastic α -particle scattering is explained within the framework of SU(3) including predominantly 1p-1h excitations. A detailed shell model calculation gives similar results. It is shown that the E2 resonance in 16O decays preferentially into the 4.43 MeV 2+ state in 12C and an α-particle in an l = 4 partial wave. A similar study in 40Ca reveals that the α- over proton-decay ratio is considerably reduced compared to the ratio for 16O reproducing the experimental trend. © 1979.