Abstrakt
High quality neutron capture and transmission data were measured on isotopically enriched Pt-192,Pt-194,Pt-195,Pt-196 and natural Pt samples at ORELA. R-matrix analysis of this data revealed resonance parameters for 159, 413, 423, 258, and 11 neutron resonances for neutron energies below 5.0, 16.0, 7.5, 16.0, and 5.0 keV for Pt-192,Pt-194,Pt-195,Pt-196,Pt-198+ n, respectively.
Earlier analysis of data on reduced neutron widths, Gamma(0)(n), showed that the distributions of Gamma(0)(n) for Pt-192,Pt-194 deviate significantly from the Porter-Thomas distribution (PTD) predicted by random matrix theory. In this contribution we report on preliminary results of the analysis of distribution of total radiation widths, Gamma(gamma) in Pt-192,Pt-194,Pt-195,Pt-196+n reactions.
Comparison of experimental data with predictions made within the nuclear statistical model indicates that standard models of Photon Strength Functions (PSFs) and Nuclear Level Density predict Gamma(gamma) distributions which are too narrow. We found that satisfactory agreement between experimental and simulated distributions can be obtained only by a strong suppression of the PSFs at low gamma-ray energies and/or by violation of the usual assumption that primary transitions from neutron resonances follow the PTD.
The shape of PSFs needed for reproduction of our Gamma(gamma) data also nicely reproduces spectra from several (n,gamma) experiments on the neighbor nuclide Au-198.