Energy Levels inPu239Populated by Electron-Capture Decay of 11.9-hAm239

Abstract

$\gamma$ singles spectra of mass-separated ${}_{}{}^{239}{}_{}{}^{}\mathrm{Am}$ (11.9 ± 0.1 h) samples have been measured with high-resolution Ge(Li) detectors. Conversion-electron spectra were measured at 0.1% resolution with a magnetic spectrometer and also with a cooled Si(Li) detector. An $M1\mathrm{}$ multipolarity was found for the weak 124.42-keV transition from the previously known 511.84-keV state to the $\frac{9}{2}+$ level at 387.42 keV. The 511.84-keV state in ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ is therefore designated as the spin-$\frac{7}{2}$ member of the $\frac{7}{2}+\left(624\right)\mathrm{}$ Nilsson state. New very weak intraband transitions (101.96 keV, $E2\mathrm{}$ and 57.3 keV, predominantly $M1\mathrm{}$) depopulating the $\frac{9}{2}+$ state at 387.42 keV support its spin assignment. Atomic electron binding energies for the $K$, $N_{1-4}$, $O_2$, and $O_3$ shells in Pu were obtained; small revisions in best values for Pu electron binding energies are suggested. $\mathrm{Log}\mathrm{ft}$ values for the electron-capture transitions ${}_{}{}^{239}{}_{}{}^{}\mathrm{Am}$ → ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$ were derived.