Recent Investigations and Findings about the 2d- and 3d- Neutron Strength Functions and the p-wave Scattering Radius

摘要

Comprehensive and detailed investigations were recently undertaken due to the scarcity of available data on the neutron d-wave strength functions and the need to obtain precise average resonance parameters for advanced technologies. This information is derived by fitting available total cross section data from few keV to 14 MeV neutron energy using the least-squares method, where the total cross section is described in terms of the scattering radius R_ℓ for various partial waves, the s-, p-, d-, f- and g- neutron strength functions, neutron penetration factors and phase shifts. The present results reveal the following findings: (ⅰ) the peak of the 2d strength function is observed for the first time at A=50; (ⅱ) due to nuclear deformation effects, the 3d-peak is depressed producing two peaks located at 152 and 170, similar to the s-wave case; (ⅲ) except for the deformed mass region, a spherical optical model calculation for the d-wave strength function reasonably describes the trend of the present data; (ⅳ) the derived s- and p-wave strength functions and the s-wave scattering radii are in good agreement with those obtained from the resolved energy region, as reported in the Atlas of Neutron Resonances; (ⅴ) the d-wave strength functions are however generally discrepant with available data; (ⅵ) several d-wave strength functions are derived here for the first time; (ⅶ) a new finding is that the p-wave scattering radii for 92 nuclei in the mass region ~(16)O - ~(242)Pu exhibit minima roughly at A (≌) 80 and 230 and maxima at A (≌) 50 and 160.