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Nuclear reactions/Fast neutrons/Activation cross-sections/Osisotopes SummaryUsing the activation technique, 14.7 MeV neutron cross sections of Os-isotopes were measured. Induced γ-activities were counted with a calibrated Ge(Li)-spectrometer. Cross-sections are given relative to σ"Α1(η, α) = 112 mb: σ 1 "Os(n, 2n)' "80s = (1449± 99) mb; a" 4 Os(n, 2n)" 3m Os = (488± 39) mb; a" 6 Os(n, 2n) 18S Os = (2004± 120) mb; σ 1 ">Os(n, a) 1 "W = (0.82±0.06) mb; σ 190 Os(n, η'γ) 19°O s = (11 ± 1.1) mb. The total (n, 2n)-cross-sections found agree with theoretical estimates, but disagree with smaller values given in the literature.

The cross-sections for e3Cu, 74Ge, 75As, s~ SlBr, I3~ mPr, lssW, ~176 7) reactions have been measured at 3 MeV. The results are in agreement with earlier measurements and follow the general trend observed in the radiative capture cross-sections for fast neutrons. In the case of Ge, Se and.Pr the isomeric cross-section ratios were also caleulated on the basis of the HUIZENCA--VANVENBOSVr method. From a comparison of the caleulated and measured isomeric ratios the probable value of the spin cut-off parameter and the inertia moment of the nucleus have been deduced. * De6icated to Prof. A. SZALAY on bis 60th b i r t h d a y .

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