Further Observations on the Production ofN13

The reactions ${\mathrm{C}}^{12}+{\mathrm{H}}^1\to {\mathrm{N}}^{13}+h\nu$ and ${\mathrm{C}}^{12}+{\mathrm{H}}^2\to {\mathrm{N}}^{13}+n^1$ have been studied and the absolute yield of positrons measured for various voltages. The proton-capture reaction shows a single resonance of 30 kv half-width at 450 kv. This resonance has been compared with the similar lithium resonance to fit it into the voltage scale of the lithium and fluorine resonances. Comparison of the positron yields of the two reactions permits a calculation of the yield of ${\mathrm{N}}^{13}$ in the proton reaction from the yield of neutrons in the deuteron reaction as measured by Amaldi, Hafstad, and Tuve. The yield thus determined is approximately 7.5 times higher than the previously accepted value based on positron measurements, and corresponds to a total reaction cross section of about 8.4×${10}^{-24\mathrm{}}$ volt ${\mathrm{cm}}^2$. However, the observed number of positrons from the deuteron reaction, obtained by comparison with uranium, is 2.5 times less than the number of neutrons from the same reaction. This discrepancy could be explained by $K$ electron capture by the ${\mathrm{N}}^{13}$ nucleus, but the errors involved are too uncertain to say definitely that this process does occur. An unsuccessful attempt was made to observe scattering of protons by carbon at the resonance voltage.