The nuclear magnetic moment of "Ir and the directional distribution of gamma rays in "Os
Angular distributions of gamma transitions between levels in I9OOs fed in the decay of I9'Ir aligned in a rhenium single crystal have been measured at temperatures down to 2 mK. Multipole mixing ratios in both gamma and electron-capture transitions are deduced and compared with various nuclear models. The angular distribution coefficients are applied to interpret very small anisotropies observed when I9'Ir is polarised in an iron host matrix, cooled to 2.5 mK. The deduced magnetic dipole moment of the 4 + ground state of I9'Ir is Ip(I9'Ir; GS)~ = 0.04( l)pN. Possible single-particle descriptions compatible with this result are suggested. NUCLEAR MOMENTS: I9'Ir (from Re(a, n)): measured I,(@ from oriented nuclei in single crystal Re and polycrystalline Fe: deduced I9OOs S(E2/M1), Jp in electron capture, lpl(1901r ground state).
Levels in Gd156 excited in the decay of 5.6 d Tb156
Abstract The decay of 5.6 day Tb 156 has been studied by means of a six gap β-ray spectrometer, scintillation spectrometers, and coincidence techniques. Conversion electron and γ-ray coincidence measurements have been used extensively for obtaining quantitative estimates of γ-ray intensities. A description of the electronic equipment is given, including a scaler and gate unit, which improves the performance of a relatively slow ( τ = 700 μ sec) multichannel analyzer. 24 transitions are assigned to Tb 156 . Multipole orders are given in most cases. The following levels are proposed and their quantum numbers ( K , I , π ) given in parenthesis: 89 keV (0, 2 + ), 199 keV (0, 4 + ), 584 keV (0, 6 + ) 1126 keV (tentative), 1152 keV (2, 2 + ), 1246 keV (2, 3 + ), 1507 keV (4, 4 + ), 1620 keV (4, 5 + ), 1931 keV (3 − ), and 2042 keV (4 − ). Violation of K -selection rules and significant deviations from the expected branching ratios for transitions to a rotational band are observed. These features are discussed in terms of a probable mixing of the rotational bands.
High spin negative parity states in doubly even Hg, Pt, and Os nuclei
Abstract A systematic study of the level structure of 200 Hg, 198 Hg, 196 Hg, 194 Pt, 192 Pt, 190 Pt, 188 Os, 186 Os and 184 Os has been performed by means of (α, 2nγ) and (p, 2nγ) in-beam γ-ray spectroscopy. Much new information has been obtained about the individual level spectra, and arguments based on level energy and population intensity systematics have been used to trace the behaviour of interesting spectral features through this series of transitional nuclei. Of particular interest is a 5 − , 7 − , 9 − … sequence of levels which appears to be a recurring feature in the spectra of the doubly even Pt and Hg nuclei in the mass range A = 190–200. These negative parity levels are connected by enhanced E2 transitions and they are very strongly populated in the de-excitation of the residual nuclei formed in (α, 2n) reactions. It is proposed that the 5 − , 7 − , 9 − … sequences constitute rotation-aligned bands analogous to the decoupled bands identified by Stephens and co-workers in odd- A transitional nuclei. In the doubly even nuclei, the bands may arise from the coupling of an i 13 2 neutron with a low- j neutron partner (from the p 1 2 , p 3 2 and f 5 2 orbitals). Negative parity levels in the Os nuclei are populated much less strongly in the (α, 2nγ) reactions. While 5 − levels corresponding to those in the Pt and Hg nuclei appear to be fairly well established in 186 Os, 188 Os (and 190 Os), it is not yet clear whether the 5 − , 7 − , 9 − … band sequence extends into the Os nuclei.