Electromagnetic radiation intensities from levels of ${\mathrm{Np}}^{237}$ were remeasured with NaI scintillation detectors and an argon proportional chamber. By absolute and coincidence counting the photon intensities per alpha particle are 0.376, 0.025, 0.00073, and 0.359 for the $L$ x-rays and the 26.4-, 43.4-, and 59.6-kev gamma rays, respectively. Gamma rays with 99- and 103-kev energy were found by $\alpha -\gamma$ coincidence. The 99-kev $\gamma$ ray is emitted from the 159-kev level with an intensity of 2.3×${10}^{-4\mathrm{}}$. The 103-kev $\gamma$ ray, of intensity 1.9×${10}^{-4\mathrm{}}$ per alpha particle, is a de-excitation of the 103-kev level. The intensity of $L$ x-rays from levels above 59.6 kev is 0.064. Coincidence intensities of 26-kev $\gamma$ rays with $L$ x-rays from conversion of the 33.2-kev $\gamma$ ray and of $L$ x-rays from these transitions are 0.01 and 0.031 per alpha particle, respectively.

• Received 6 March 1957

DOI:https://doi.org/10.1103/PhysRev.107.161