Levels inU239

Abstract

Thirty-seven levels have been observed in ${}_{}{}^{239}{}_{}{}^{}\mathrm{U}$ up to an excitation energy of 1692 keV with 12-MeV deuterons and the reaction ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}\mathrm{}(d,p)\mathrm{}{}_{}{}^{239}{}_{}{}^{}\mathrm{U}$. The ground-state $Q$ value was determined as 2579±7 keV. A germanium detector, operated as a pair spectrometer for high-energy capture gamma rays and as a total-energy anticoincidence spectrometer for low-energy gamma rays, has been used to measure 27 high-energy transitions between 3150 and 4850 keV and 27 low-energy transitions between 490 and 900 keV. Analysis of the combined data suggests fairly definite assignments for 13 states below 373 keV. The presence of the 152-neutron energy gap is clearly indicated by the absence of states between 373 and 692 keV. From 692 keV upward, nine additional tentative assignments are made. The spectroscopic assignments are [band-head energy (keV) in parenthesis, followed by spin, parity, and (in brackets) asymptotic quantum numbers]: (ground state), $\frac{5}{2}+\left[622\right]\mathrm{}$ with superimposed rotational band to 11/2+; (133),½+[631] with rotational band to $\frac{9}{2}+$; (∼173), $\frac{7}{2}+\left[624\right]\mathrm{}$ with rotational band to 13/2+; (692), ½+[620] with rotational band to $\frac{5}{2}+$, and (742),½-[761] with anomalous rotational spacings to 11/2-. A table of $C_{j,l}$ values for deformation $\beta$ of 0.20, 0.25, and 0.30 is presented in the Appendix for all Nilsson orbitals of interest in the actinide region. The relative intensities or signatures of the bands are found for the most part to be in good agreement with theory. Absolute magnitudes are a factor of 2 too high. This discrepancy is ascribed to Coulomb stripping effects.