Distribution of Radiative Strength in GD-156, 157 and 158 Nuclei

摘要

The distribution of E1 and M1 strength in (156,157,158) Gd compound nuclei hasbeen studied. The authors compare several formulations of strength functions to average resonance capture and/or photoabsorption data. Further they use these prescriptions in calculations of the total average radiation width, radiative capture cross sections and gamma-ray spectra, and compare them to available experimental information. As the calculated quantities critically dependon the magnitude and energy dependence of the gamma-ray strength functions, the results can be used to test the validity of their models. By analyzing the results for (155,156,157) Gd(n,gamma) reactions strong evidence was found for an E1 strength function which is based on a generalized Lorentzian, enhanced compared to spherical nuclei, with an energy dependent spreading width and a nonzero limit as the energy tends to zero. For M1 radiation the giant resonance spin-flip mode is favoured. The possibility of inclusion of a M1 scissors excitation at around 3.MeV in (156) Gd is discussed.