Gamma Transitions Feeding the 4-msec,132+Level ofPb205in the Decay ofBi205

Abstract

The decay of 14.5-day $^{205}\mathrm{Bi}$ has been reexamined, using delayed coincidence techniques, to establish which of the known $\ensuremath{\gamma}$-ray transitions feed the 4-msec, $\frac{13}{{2}^{+}}$ isomeric level in $^{205}\mathrm{Pb}$. The 987.8-keV transition in $^{205}\mathrm{Pb}$ was used as a signature for the decay of the $\frac{13}{{2}^{+}}$ level. The data indicate that three transitions of energy 580.0, 1208.3, and 1552.2 keV, with respective relative intensities of 17.4, 7.6\ifmmode\pm\else\textpm\fi{}1.1, and 6.1\ifmmode\pm\else\textpm\fi{}0.8, are in delayed coincidence with the 987.8-keV transition. The sum of these transition intensities is in good agreement with the summed intensity of all transitions known to depopulate the isomeric level. In addition, prompt coincidence data indicate that the 550.1-keV transition feeds the 1043.7-keV level of $^{205}\mathrm{Pb}$. Evidence is presented that the 1043.7-keV level is ${\frac{7}{2}}^{\ensuremath{-}}$ instead of the previous assignment of ${\frac{5}{2}}^{\ensuremath{-}}$.