The absolute ($\gamma , p_0$) differential cross sections for ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ were measured at bremsstrahlung end point energies between 17 and 25 MeV. Using an artificially constructed pseudomonoenergetic photon spectrum, absolute cross sections for various semidirect photoproton reaction channels were also determined. The general structure in the total ($\gamma , p$) cross section is discussed in terms of isospin and deformation effects. The direct, preequilibrium and equilibrium contributions to the photoproton decay of the giant dipole resonance equal about 35, 20, and 45%, respectively, of the total energy-integrated ($\gamma , p$) cross section. Comparison is made with the predictions of the exciton model.

NUCLEAR REACTIONS ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}(\gamma , p)$, $E=15.6-25\mathrm{}$ MeV, $\theta =37\mathrm{}°-143\mathrm{}°$; measured $\sigma (E; \theta )$ absolutely. Deduced $\sigma (E; p_i)$, $\sigma \mathrm{}\left(E\right)\mathrm{}$, direct-semidirect cross section, isospin splitting, preequilibrium decay. Natural target.

• Received 1 April 1982

DOI:https://doi.org/10.1103/PhysRevC.26.448