Study of Nuclear Structure Parameters by Using the (n_th,2_γ) Reaction

The empirical Dubna model for investigating of the cascade gamma-decay of the neutron resonance allows a simultaneous determination of the level density and radiative strengths in a region up to the binding neutron energy for any nucleus. Data can be obtained by determining the intensities of two-step cascades between a decaying compound-state and a group of low-lying levels of the nucleus and describing these intensities by using the most appropriate models prescribed parametrically. For evaluation and minimization of systematical errors of the models used for the level density and radiative strengths for primary gamma transitions spectroscopic information about quanta sequence for observed resolved cascades must be obtained and at least two different sets of models must be used for verifiation of derivable nuclear parameters. The step-wise structure, which was observed in the energy dependence of the level density for more than 40 investigated nuclei, shows that the structure of a nucleus modifies by excitation.