Thermal Neutron Capture Cross Section of Carbon-13

The thermal neutron capture cross section of C¹³ has been determined from the amount of C¹⁴ formed in pile-irradiated samples of graphite, barium carbonate, and carbon dioxide. Because of the impurity reaction, N¹⁴(n, p)C¹⁴, of comparatively high cross section, the results were consistent only when samples were used which were enriched in C¹³.The average isotopic cross section determined for the enriched samples was 1.4±{}0.2 millibarns. The final value of the cross section in these samples corrected for the estimated residual nitrogen impurity is 0.9±{}0.2 millibarn.