Excitation-energy spectra resulting from the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(γ,p) reactions at 90° have been measured with tagged photons of about 61 and 77 MeV. Decay to several discrete states is discussed. Evidence is shown for an absorption process where the photon interacts with a T=1 proton-neutron pair, instead of the T=0 p-n pair implicit in the quasideuteron model.

• Received 12 March 1990

DOI:https://doi.org/10.1103/PhysRevC.42.R1179