Gamma-Ray Absorption in Carbon

The total absorption in carbon of the gamma rays from the ${\mathrm{T}}^3(p, \gamma ){\mathrm{He}}^4$ reaction was measured as a function of proton energy and hence gamma-ray energy. As the gamma-ray energy was varied from 20.3 to 20.8 Mev, the total absorption cross section in carbon varied smoothly from 315±5 to 324±6 millibarns. The resolution was better than 70 kev and the sensitivity sufficient to detect narrow resonances of more than 0.8 Mev-millibarns integrated cross section, but no structure was observed although photonuclear resonances have been reported in this region.