In-beam, time-sorted measurements of internal conversion electrons and $\gamma$ rays are reported for ${}_{}{}^{203}{}_{}{}^{}\mathrm{Pb}$ formed by the ${}_{}{}^{204}{}_{}{}^{}\mathrm{Hg}$($\alpha$,$5n$) reaction at $E_{\alpha }=53.5\mathrm{}$ MeV. The multipolarity of the 153 keV transition deexciting the $\frac{29}{2^{-}}$ isomer is determined to be $E3$. The 239-keV transition, in the cascade connecting the $\frac{23}{2^{+}}$ and $\frac{21}{2^{+}}$ states, is determined to be $M1$. The 874-keV transition is found to have an $\frac{M1}{E2\mathrm{}}$ $\gamma$ intensity ratio of ${0.4}_{-0.15\mathrm{}}^{+0.20\mathrm{}}$. Thus, the state at 2796 keV is assigned $J^{\pi }=\frac{23}{2^{+}}$ and has a probable configuration ${p_{\frac{1}{2}}}^{-1\mathrm{}}{f_{\frac{5}{2}}}^{-3\mathrm{}}{i_{\frac{13}{2}}}^{-1\mathrm{}}+{p_{\frac{1}{2}}}^{-2\mathrm{}}{f_{\frac{5}{2}}}^{-1\mathrm{}}{f_{\frac{7}{2}}}^{-1\mathrm{}}{i_{\frac{13}{2}}}^{-1\mathrm{}}$. The other measured multipolarities are $E2\left(258 \mathrm{keV}\right)$, $M1\left(635\mathrm{} \mathrm{keV}\right)$, $E2\left(839\mathrm{} \mathrm{keV}\right)$, and $M4\left(1027\mathrm{} \mathrm{keV}\right)$ with no measurable admixture of multipoles.

NUCLEAR REACTIONS ${}_{}{}^{204}{}_{}{}^{}\mathrm{Hg}$($\alpha$,$5n$)${}_{}{}^{203}{}_{}{}^{}\mathrm{Pb}$, $E_{\alpha }=53.5\mathrm{}$ MeV. Measured $\gamma$ and conversion electron spectra 30-1300 keV in eight time bands between beam bursts. Deduced ICC, $J$, $\pi$. Si(Li) and Ge(Li) detectors.

• Received 8 June 1978

DOI:https://doi.org/10.1103/PhysRevC.20.546