Inelastic Nuclear Scattering of Photons byAu197

A lower limit of the total inelastic nuclear photon scattering cross section of Au was determined as a function of energy by measuring the yield of the reaction ${\mathrm{Au}}^{197}(\gamma , {\gamma }^{\prime }){\mathrm{Au}}^{197m}$ (7.5 sec) as a function of betatron energy. The use of pneumatic transfer and of NaI-counters in good geometry with 16-gram gold disks as samples enabled one to obtain good counting statistics and detailed decay curves at all betatron energies between 4 and 24 Mev. It is found that the cross section falls off steeply as soon as the competition from the ($\gamma , n$) reaction becomes possible. The maximum cross section of about 3.5 mb is reached at (7.8±0.2) Mev. This disagrees with earlier work of Cameron and Katz but corresponds qualitatively to the same behavior as exhibited by ${\mathrm{In}}^{115}(\gamma , {\gamma }^{\prime }){\mathrm{In}}^{115m}$ in the recent work of Burkhardt et al. Our results indicate a second peak of the cross section at about 15 Mev, where the giant resonance has its maximum, in agreement with recent work of Hayward and Fuller on elastic scattering from gold.