The Total Cross Section of theHe3Nucleus for Slow Neutrons

Using the slow neutrons available from the thermal column of the enriched uranium pile of this Laboratory, the total cross section of the ${\mathrm{He}}_3$ nucleus was determined by the transmission method. To the precision of the data, this cross section obeys the $\frac{1}{v}$ law in the range of averaged neutron energies extending from about 0.001 to 0.03 electron volt. The product ($\sigma {\mathrm{He}}_3\times v$) is found to be (11.2±0.5)×${10}^6$ barns×meters×${\sec .\mathrm{}}^{-1\mathrm{}}$. The possible theoretical implications of these results are briefly discussed in connection with the properties of the compound ${\mathrm{He}}_4$ nucleus.