Excitation Function for theV51(γ, α)Sc47Reaction

Yields of the ${\mathrm{V}}^{51}(\gamma , \alpha ){\mathrm{Sc}}^{47}$ reaction have been determined by measuring the ${\mathrm{Sc}}^{47}$ radioactivity produced in metallic vanadium targets irradiated with bremsstrahlung of maximum energy varying from 10.5 to 25 Mev. The reaction was not observed below 15.5 Mev because of the severe effect of the Coulomb barrier on the outgoing alpha particles. The excitation function derived from these measurements has a maximum value of 0.81 mb at 23 Mev, and the integrated cross section to 24.5 Mev is 4.3 Mev-mb. The observed excitation function agrees very well with one calculated from a statistical theory for the decay of a compound nucleus. This appears to be a general feature of ($\gamma , \alpha$) reactions in medium-weight nuclei.