New Gamma Rays in the Neptunium-239 Decay

Abstract

Two unreported gamma rays of energy 0.44 and 0.49 Mev are assigned to ${\mathrm{Np}}^{239}$ by reason of chemical properties and decay constant. The intensities of these gamma rays relative to a previously reported ${\mathrm{Np}}^{239}$ gamma at 0.334 Mev have been determined to be ${\gamma }_1\left(0.33\mathrm{} \mathrm{Mev}\right):{\gamma }_2\left(0.44\mathrm{} \mathrm{Mev}\right):{\gamma }_3\left(0.49\mathrm{} \mathrm{Mev}\right)=100:0.40:0.50\mathrm{}$. Measured yields (gamma rays per decay) for the 0.44- and 0.49-Mev gammas are 1.6×${10}^{-4\mathrm{}}$ and 1.9×${10}^{-4\mathrm{}}$ gamma rays per decay. It seems probable that both of these gamma rays originate from a single ${\mathrm{Pu}}^{239}$ level at 0.49 Mev.