Delayed Neutrons fromPu239

The shape of the decay curve of ${\mathrm{Pu}}^{239}$ delayed neutrons is found to be very nearly the same as that of ${\mathrm{U}}^{235}$. The ratio of the relative number of delayed neutrons in ${\mathrm{Pu}}^{239}$ to that in ${\mathrm{U}}^{235}$ was found to be 0.47 for neutrons delayed over 2 seconds and 0.40 for neutrons delayed over 5 seconds. In the light of the experimental errors, it is questionable whether these numbers are significantly different.