Os186studied in the decay of 15.8-hIr186and by theW186(α, 4n)Os186reaction

Abstract

New information about levels in the transitional nucleus /sup exclamation-point86/Os is gained from a study of the decay of 15.8-h /sup 186/Ir. A significantly improved decay scheme was deduced from an extensive ..gamma..-..gamma.. 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 ..gamma.. band were confirmed, up to I = 6. In addition, detailed evidence for the existence of a K = 0 band, built upon the known 0/sup +/ level at 1061 keV, is presented (2/sup +/,4/sup +/, and 6/sup +/ 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 ..mu../sub N/ for the magnetic moment of /sup 186/Ir is reported, and is discussed in terms of coupling of Nilsson states; the assignment )7/2/sup +/(404)..pi..; 3/2/sup -/(512)..nu..)5/sup -/ is proposed. Results of a study of the /sup 186/W(..cap alpha..,4n)/sup 186/Os reaction, including ..gamma.., ..gamma..-..gamma.., ..gamma..more » (theta), and ..gamma..-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.« less