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).
Nuclear orientation of 188-189Ir and 189-191Pt
188-189Ir and 189-191Pt have been oriented at low temperature in the hyperfine magnetic field in iron. Precise energy measurements of some high-energy gamma rays in the disintegration of 188Ir have also been performed, resulting in the modification of the high-energy level scheme of 188Os. In the daughter nuclei spins and parities of excited states and multipole mixing ratios of transitions are established. For some non-unique electron-capture transitions jbeta =0/jbeta =1 intensity ratios are also deduced. Results are analysed in terms of mixed p3/2 and f5/2 configurations in the neutron shell.
Studies of Decay Schemes in the Osmium-Iridium Region. II. Decay of 12-Day Ir 190
Spectra of the gamma rays and internal conversion electrons emitted in the decay of 12-day Ir/sup 190/ were studied in detail. Internal conversion spectra were obtained with the aid of double-focusing and intermediate-image BETA spectrometers and a permanent-magnet spectrograph. Gamma spectra were obtained by means of photoelectric conversion, employing a double-focusing spectrometer, and by scintillation techniques. These measurements of the energies and relative intensities of gamma rays and internal conversion electrons give internal conversion coefficients for a number of transitions. These data, coupled with coincidence studies of gamma rays, support the level scheme reported by Nielsen et al. for Os/sup 190/ and establish new, oddparity levels at 1384, 1568, and 1876 kev. An upper limit of 2 x 10/sup -5/ is set on positron branching in the decay of Ir/sup 190/. Relative electron capture transition probabilities for the decay of Ir/sup 190/ to Os/sup 190/ and ratios of reduced transition probabilities for electromagnetic transitions from a number of levels of Os/sup 190/ follow from these results. They are compared with the predictions of the strong-coupling model and the asymmetric rotor model. The half life of Ir/sup 190/ was found to be 12.3 plus or minus 0.4 days. Even-A iridium-osmium totalmore » disintegration energies were found to rise substantially above the values predicted by semiempirical mass formulas; this suggested a possible effect of the change in the nuclear deformation in this region. (auth)« less