The Complex Alpha-Spectra ofAm241andCm242

Abstract

The alpha-particle spectra of ${\mathrm{Am}}^{241}$ and ${\mathrm{Cm}}^{242}$ was studied in detail utilizing a 75-cm radius of curvature 60° symmetrical electromagnetic analyzer with photographic plate detection. The radioactive sources containing up to 3 μg/${\mathrm{cm}}^2$ of active atoms in the case of ${\mathrm{Am}}^{241}$ were prepared by vacuum sublimation. The average geometry of the spectrograph is about 4 parts in ${10}^5$. The energy dispersion on the photographic plate is about 3.4 kev/mm for 5-Mev alpha-particles, and the width at half-maximum of these alpha-particle groups is about 7 kev. Six alpha-particle groups were found in ${\mathrm{Am}}^{241}$, and their energies and abundances are 5.546 Mev, 0.23 percent; 5.535, 0.34 percent; 5.503, 0.21 percent; 5.476, 84.2 percent; 5.433, 13.6 percent; 5.379, 1.42 percent. In ${\mathrm{Cm}}^{242}$ two alpha-particle groups were found whose energies and abundances are 6.110 Mev, 73 percent, and 6.064, 27 percent. The alpha-decay scheme is correlated with gamma-rays and conversion electrons observed in this laboratory for both ${\mathrm{Am}}^{241}$ and ${\mathrm{Cm}}^{242}$. The various alpha-groups are evaluated with respect to the alpha-decay systematics, and the degrees of hindrance of the various alpha-transitions are discussed with reference to normal trends in even-even nuclei. It is suggested that the totally different patterns of the spectra of the two nuclides are conditioned by the nuclear types.