Photoreactions of 12C, 16O and 40Ca in self–consistent RPA theory

The photoreactions of 12C, 16O and 40Ca from particle threshold up to 80 MeV are analysed in the frame of a self-consistent RPA theory with Skyrme interactions. The excitation of the E1 and E2 giant resonances is shown in the energy continuum by referring to photoabsorption (γ, p) and (γ, n) decay channels. The calculations are performed with a Skyrme III force for its better founded momentum dependence. Correlations between the nuclear dynamics and the properties of the interaction in the spin-spin channel, momentum and density dependence are pointed out. In this connection, an estimate is made of the MEC contribution included in RPA calculations by using Siegert's theorem in the electric transition operator. The E2 decay in (γ, p) and (γ, n) channels predicted by the RPA is compared with experimental observations of (α, α′), (γ, γ), (γ, n) and (p, γ) reactions.