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Cross sections for the 174Hf(n, 2n)173 Hf and 176Hf(n, 2n)175Hf reactions have been measured on the 5.5-MV Van de Graaff tandem accelerator of National Centre for Scientific Research "Demokritos" in Athens, in the neutron energy region from 8.8 to 11.0 MeV, using the activation technique. An experimental method to account for the contamination of the 176Hf(n, 2n) reaction by the 176Hf(n, λ) reaction activated by the parasitic neutrons of the beam is presented. Statistical model calculations have also been performed using the nuclear-reaction codes EMPIRE-II and TALYS. The results and effects of the nuclear input parameters as well as pre-equilibrium emission are discussed in detail. [ABSTRACT FROM AUTHOR]

In the present work, the 197Au(n,2n) reaction cross section is experimentally determined relative to the 27Al(n,α)24Na reaction at incident neutron energies of 9.0-10.5 MeV by means of the activation technique. The quasimonoenergetic fast neutron beam was produced via the 2H(d,n)3He reaction at the 5.5-MV Tandem Van de Graaff accelerator at the National Centre of Scientific Research (NCSR) "Demokritos" and was studied to determine the contribution of background "parasitic" neutrons using the multiple foil activation technique and the SULSA unfolding code. The cross sections for the population of the second isomeric state (12-) of 196Au and the sum of the ground (2-) and first isomeric state (5-) population cross sections were independently determined. Auxiliary Monte Carlo simulations were performed with the MCNP code. Theoretical calculations of the above cross sections in the 8-25 MeV region were carried out with the use of the STAPRE-F, EMPIRE, and TALYS codes, which were also compared in their implementation of the generalized superfluid model. The theoretical results are compared with previous work in the same mass region, and the strong dependence on the level scheme of the nuclei involved was revealed. [ABSTRACT FROM AUTHOR]

Recent accurate data obtained for the isomeric cross section of the 197Au(n, In) reaction provide a valuable opportunity to consider the question of the effective moment of inertia of the nucleus within a local consistent model analysis of all available reaction data for the 197Au target nucleus. Thus, a definite proof of a moment of inertia equal to that of the rigid-body has been obtained for the 196Au nucleus, while indications infer about half the rigid-body for 194Ir. [ABSTRACT FROM AUTHOR]