Long-Lived Radioactive Carbon:C14

A long-lived activity has been obtained by deuteron bombardment of graphite. This activity has been shown by chemical methods to be isotopic with carbon. The same activity has been obtained by slow neutron irradiation of nitrogenous compounds (N${\mathrm{H}}_4$N${\mathrm{O}}_3$, N${\mathrm{H}}_4$N${\mathrm{O}}_2$, etc.). The radiations consist of low energy negative electrons with a range of 19±2 mg/${\mathrm{cm}}^2$ aluminum (145±15 kev upper energy limit). No soft or hard gamma-rays could be detected. The nuclear reactions must be ${\mathrm{C}}^{13} \mathrm{}(d,p)\mathrm{} {\mathrm{C}}^{14}$ and ${\mathrm{N}}^{14} \mathrm{}(n,p)\mathrm{} {\mathrm{C}}^{14}$. A sample has been followed in a screen wall Geiger counter for 9 months and has shown no decay. From cross section and yield estimates the half-life of ${\mathrm{C}}^{14}$ is probably ${10}^3$-${10}^5$ years. The production, isolation, and detection of ${\mathrm{C}}^{14}$ for tracer work is described.