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Os-186 studied in the decay of 15.8-h Ir-186 and by the W-186 (alpha, 4n) Os-186 reaction

  • Spanhoff, R.
  • Postma, H.
  • Canty, M.J.
Publication Date
Jul 01, 1978
DOI: 10.1103/PhysRevC.18.493
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New information about levels in the transitional nucleus Os186 is gained from a study of the decay of 15.8-h Ir186. A significantly improved decay scheme was deduced from an extensive γ−γ coincidence measurement. Spins and parities were determined for many levels from a nuclear orientation study; in several cases measured electron-conversion data were useful. Spins for the proposed members of a γ band were confirmed, up to I=6. In addition, detailed evidence for the existence of a K=0 band, built upon the known 0+ level at 1061 keV, is presented (2+, 4+, and 6+ members at 1209, 1461, and 1813 keV, respectively). Mixing ratios for interband transitions depopulating the members of both bands were determined from the nuclear orientation data, and are discussed. The deduced E2 branching ratios are fairly well reproduced in a band-mixing calculation incorporating these bands. An absolute value of (2.8±0.3) μN for the magnetic moment of Ir186 is reported, and is discussed in terms of coupling of Nilsson states; the assignment {72+[404]π; 32−[512]ν}5− is proposed. Results of a study of the W186(α, 4n)Os186 reaction, including γ, γ−γ, γ(θ), and γ−t measurements, confirm the results of the decay study. In addition, two isomeric states were identified, at 1774 keV (8.1 ns) and at 2165-keV (5.3 ns). Side-feeding of negative parity levels was observed. RADIOACTIVITY Ir186 (15.8-h isomer); measured Iγ(θ) oriented nuclei; γ−γ coin; ICC. Os186 deduced levels; Jπ, mixing ratios; band-mixing calculation. Ir186 deduced magnetic moment, Nilsson assignment. NUCLEAR REACTIONS W186(α, 4n)Os186, Eα=47 MeV; measured Eγ, Iγ, γ−γ coin, Iγ(θ), γ−t; Os186 deduced levels, Jπ, T12.

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