U238(n,γ)U239and States ofU239

The high-energy regions of the $\gamma$-ray spectra formed by thermal-neutron capture and by average resonance capture were measured with an annihilation-pair Ge(Li) spectrometer. The observed $\gamma$-ray lines reveal the presence of many new states in ${}_{}{}^{239}{}_{}{}^{}\mathrm{U}$, and the intensities of lines in the average resonance-capture spectra establish the parties and limit the spins of the states. The data are entirely consistent with what is expected from the set of single-particle configurations used by Braid et al. to interpret the states of four odd-$A$ curium isotopes - i.e., all states with excitation energies less than 890 keV are interpretable in terms of these configurations, and no unobserved states are predicted. The average widths of $E1\mathrm{}$, $M1\mathrm{}$, and $E2\mathrm{}$ transitions are compared with the results of other experiments and with theory. The average $E1\mathrm{}$ and $M1\mathrm{}$ widths are consistent with what is expected, but the average $E2\mathrm{}$ width is unusually large. The unusual strength of one $E1\mathrm{}$ transition is discussed. The relationship between the branching ratios for thermal-neutron capture and for resonance capture is discussed in an appendix.