 Bacher was able to report that the number of neutrons per fission of plutonium-239 was 2.64 ± 0.2, about 1.2 times as much as uranium-235.Titterton and Boyce McDaniel of Wilson's P-1 (Cyclotron) Group attempted to measure the time it took for prompt neutrons to be emitted from a uranium-235 nucleus when it fissions.They calculated that most were emitted in less than 1 nanosecond.