High-spin levels in /sup 191/Pt and /sup 193/Pt and the triaxial rotor model

The high-spin level structures of the transitional nuclei /sup 191/Pt and /sup 193/Pt have been studied by (..cap alpha..,3n..gamma..) reactions on enriched Os targets. The measurements included ..gamma..-ray singles, comprehensive ..gamma..-..gamma.. coincidences, half-life determinations, and ..gamma..-ray angular distributions. The extensive /sup 191/Pt and /sup 193/Pt level schemes established are reported here. In both nuclei, decoupled ..nu..i/sub 13///sub 2/ /sup -1/ bands, strongly resembling the ground bands of the adjacent core nuclei, and many other high-spin positive parity states have been located. Low-lying 21/2/sup -/ bands have also been observed in both nuclei and they are described as semidecoupled bands with microscopic structures dominated by three-quasiparticle components of the type (..nu..i/sub 13///sub 2/ /sup -2/,..nu..j/sup -1/). The abundant information about ..nu..i/sub 13///sub 2/ level families obtained in these experiments and in a complementary /sup 191/Au decay study is discussed, and it is shown that these complex level spectra can be accounted for rather well in terms of the coupling of an i/sub 13///sub 2/ neutron hole to a triaxially deformed core. (AIP)