The electron capture decay scheme of ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ (73 min) has been investigated by measuring the $\gamma$-ray and conversion-electron spectra of mass-separated ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ samples. The $\gamma$-ray spectra were measured with a Ge(Li) spectrometer and the conversion-electron spectra were measured with a cooled Si(Li) detector and a magnetic $\beta$-ray spectrometer. Thirty-five $\gamma$ rays were identified and the multipolarities of most of the transitions were deduced. The half-life of ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ was determined by following the decay of the 280.2 keV photopeak and was found to be 73.0 ± 1.0 min. The $\alpha$-particle energy and $\alpha$ branching were measured to be 6.042 ± 0.005 MeV and [(2.5 ± 0.3) × ${10}^{-2\mathrm{}}$]%, respectively. On the basis of the present investigation the following single-particle states have been identified in ${}_{}{}^{237}{}_{}{}^{}\mathrm{Pu}$: $\frac{7}{2}-\left[743\right], 0$ ½+[631], 145.5; $\frac{5}{2}+\left[622\right], 280.2$; $\frac{3}{2}+\left[631\right], 370.4$; $\frac{5}{2}+\left[633\right], 407.8$; $\frac{7}{2}+\left[624\right], 473.5$; $\frac{5}{2}-\left[752\right], 655.3$; and $\frac{7}{2}+\left[613\right], 908.8$ keV. The ground state of ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ has been deduced to be the $\frac{5}{2}-\left[523\right]\mathrm{}$ Nilsson orbital. The $log\mathrm{ft}$ values for electron capture transitions to the observed states were derived. The $\alpha$-particle spectrum of a mass-separated ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$ sample was measured with the Argonne double focusing magnetic spectrometer. Eleven $\alpha$ groups identified in this spectrum populate the members of the ground state, ½+[631], and $\frac{3}{2}+\left[631\right]\mathrm{}$ bands. The $\alpha$-decay hindrance factors are consistent with the Nilsson-state assignments deduced from ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ electron capture decay.

RADIOACTIVITY ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ [from ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}(\alpha , 4n)$ and ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}({}_{}{}^3{}_{}{}^{}\mathrm{He}, 3n)$)]; measured $T_{\frac{1}{2}}$, $E_{\alpha }$, $E_{\gamma }$, $I_{\gamma }$, $E_{\mathrm{ce}}$, $I_{\mathrm{ce}}$, $\gamma \gamma$- coin, $\alpha$ branching, ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$ [from ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}(\alpha , 2n)$]; measured $E_{\alpha }$, $I_{\alpha }$; deduced hindrance factors. ${}_{}{}^{237}{}_{}{}^{}\mathrm{Pu}$ deduced levels $log\mathrm{ft}$, (EC) $\gamma$ multipolarity, $I$, $\pi$, eight single-particle states. Mass-separated ${}_{}{}^{237}{}_{}{}^{}\mathrm{Am}$ and ${}_{}{}^{241}{}_{}{}^{}\mathrm{Cm}$. Toroidal $\beta$ spectrometer at 0.15% FWHM.

• Received 21 April 1975

DOI:https://doi.org/10.1103/PhysRevC.12.541