Electron-Capture Decay ofAm239andAm240

The conversion electron spectra arising from electron-capture decay of ${\mathrm{Am}}^{239}$ and ${\mathrm{Am}}^{240}$ have been studied with a 180° photographic spectrograph at ∼0.1% resolution. The ${\mathrm{Am}}^{239}$ spectrum and the multipolarity data obtained therefrom are similar to those observed from the beta decay of ${\mathrm{Np}}^{239}$, but the electron intensity data indicate somewhat different relative populations of the ${\mathrm{Pu}}^{239}$ excited states in the two cases. An attempt to assign the spin and parity of ${\mathrm{Am}}^{239}$ from $\mathrm{ft}$ values by the use of $\Delta I$ and $\Delta K$ selection rules does not give a consistent explanation.