The cross section for the production of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ activity by bombarding ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ with 30 MeV electrons has been measured absolutely. The result, 11.9 ± 0.2 μb, has a smaller absolute error than any previous measurement. This value corresponds to a ($\gamma ,n$) cross section integrated to 30 MeV of 41.0 ± 0.6 MeV mb, based on a distorted-wave Born-approximation electric dipole virtual photon spectrum.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(e,n)\mathrm{}$, $F_e=30\mathrm{}$ MeV, $\sigma \mathrm{}(e,n)\mathrm{}$ measured absolutely.

• Received 18 October 1977

DOI:https://doi.org/10.1103/PhysRevC.17.1531