Abstract
The importance of narrow, isolated, resonances in the photonuclear absorption cross sections of C and O was investigated by means of an absorption experiment performed with 30.7-Mev bremsstrahlung. The experiment yielded values for the cross sections averaged over the () cross sections for and . The results for C were the same as those expected for a cross section without narrow resonances, while for O a definite resonance effect was demonstrated. The O photonuclear absorption cross section, averaged over the cross section, was found to be 26.7±3.5 millibarns, 16±4 millibarns higher than the value expected if narrow resonances contribute insignificantly. Estimated values for the parameters of the O resonances near 22 Mev are: average peak height, 106±14 mb; ratio of the radiative width (to ground state) to total width, (6.6±0.9)×; total width about 30 kev. The experimental results are insensitive to uncertainties in the non-nuclear x-ray attenuation cross sections for C and O.
- Received 15 January 1959
DOI:https://doi.org/10.1103/PhysRev.114.1324
©1959 American Physical Society