Short-Period Delayed Neutrons from Fission

A new group of delayed neutrons having a mean-life of 216±60 milliseconds has been observed to follow fission of ${\mathrm{U}}^{235}$. The apparent yield is 2.7±0.7 percent of the delayed neutrons. The experiment was done using a multiplying assembly of uranium metal bombarded once every 30 seconds by x-rays from a betatron. A discussion is given of the hypothesis that these delayed neutrons follow the decay of ${\mathrm{Li}}^9$, and that ${\mathrm{Li}}^9$ is formed as the light fragment in ternary fission.