The Alpha-Spectra ofPu239andPu240

Abstract

Utilizing a magnetic alpha-particle spectrograph the complex alpha-spectrum of ${\mathrm{Pu}}^{239}$ was found to consist of three groups: ${\alpha }_0$ (69 percent), ${\alpha }_{13}$ (20 percent), and ${\alpha }_{51}$ (11 percent). The spectrum of ${\mathrm{Pu}}^{240}$ consisted of two groups, ${\alpha }_0$ (76 percent) and ${\alpha }_{44}$ (24 percent). The nomenclature ${\alpha }_x$ refers to that alpha-group which leaves the product nucleus with an energy of $x$ kev above the ground state. The alpha-particle energy of ${\alpha }_0$ of ${\mathrm{Pu}}^{239}$ was measured as 5.150±0.002 Mev and that of ${\mathrm{Pu}}^{240}$ as 5.162±0.004 Mev. These values are correlated with the gamma-rays and conversion electrons observed by other workers to form a partial decay scheme.