Estimate of the cross section for thermal neutrons

Cross section of the thermal neutrons is considered in the framework of the statistical approach to the complicated nuclei. The probability distribution ?(z = σ/σ*) to have given cross section σ (determined by fluctuations of resonance positions and widths), where σ* is the cross section for the model of equidistant resonances with the same width, has been calculated. The last quantity can be represented in terms of the neutron strength function for given nuclei. The probability distribution ?(z) is universal for all nuclei.