Excitation cross-section of sup(78,80,82)Se two-phonon vibrational states in (nn') reactions near threshold

γ-radiation measurements of the energy dependence of cross sections for four levels of sup(78,80,82)Se treated in terms of vibrational model as two-phonon excitations, are carried out. By monitoring the energy of γ-radiation and thresholds of its appearance it is possible to identify the number of lines as transitions in even isotopes of sup(78,80,82)Se. Measurement error for relative γ-intensities is of 5-10% (in the case of neutron energy above the level excitation threshold > 100 keV). The error in cross sections values produced by normalization, is of 15%. Experimental and calculational cross sections are plotted as a function of the difference in neutron energy (in the center-of-mass system), and the level excitation energy. The cross sections are calculated according to statistic theory, by making use approximation of nonoverlapping resonances, Hauser-Feshbach formula, and an assumption for independent production of the compound nucleus decay for describing cross-sections and two variants of an optical potential. From the analysis of obtained data it follows that an assumption of statistic theory about the independent reaction channels leads to the disagreement between experimental and theory. The best correspondence of experimental and Hauser-Feshbach formula calculation results (for a small number of channels) may be considered as an evidence of correlation between partial widths of neutron resonances