We calculate the total cross sections for different multiple transitions in photon absorption in a ${}_{}{}^1{}_{}{}^{}$${\mathit{S}}_0$ pp pair embedded in a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ nucleus. Employing two models, one involving only nucleon degrees of freedom, the other in addition the Δ(1232) isobar, we show that the Δ gives important effects even in transitions where the photon cannot couple directly to the isobar.

• Received 16 December 1994

DOI:https://doi.org/10.1103/PhysRevC.51.2841