Interpolative formulae for average nuclear level spacing and total radiation width

Abstract

The free gas model formula for nuclear level densities was used to interpolate unknown level spacings. The level density parameter was fitted semi-empirically to give good fits to all experimentally measured level spacings. A formula for total radiation width is given which relates this quantity to the mass number, the average level spacing and the excitation energy. Compound nuclei which have a long-lived isomeric state were found to have, on average, a radiation width 25 percent less than for non-isomeric compound nuclei. No correlation between radiation widths and neutron strength function was observed within the limits of accuracy of the experimental data, contrary to some previous suggestions. Tables of calculated and measured resonance parameters are given for target nuclei in the range 60 < A < 203. The calculated 30 keV capture cross section is compared with measured and semi-empirical data (Allen et al. 1970) and with the calculated values of Benzi and Reffo (1969).