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

The high-spin level structures of the transitional nuclei 191Pt and 193Pt have been studied by (α,3nγ) reactions on enriched Os targets. The measurements included γ-ray singles, comprehensive γ-γ coincidences, half-life determinations, and γ-ray angular distributions. The extensive 191Pt and 193Pt level schemes established are reported here. In both nuclei, decoupled νi13/2-1 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- 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 (νi13/2-2,νj-1). The abundant information about νi13/2 level families obtained in these experiments and in a complementary 191Au 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 i13/2 neutron hole to a triaxially deformed core