ИСТИНА

New cross sections of photoneutron reactions 52Cr(g,2n)50Cr, 68Zn(g,1n)67Zn and 8Zn(g,2n)66Zn not determined before experimentally were obtained at the first time using the experimental-theoretical method for evaluation of photoneutron partial reaction cross section meeting physical criteria of reliability method. This method was proposed to solve the problem of significant disagreements between the results of experiments carried out using the beams of quasimonoenergetic annihilation photons and the method for photoneutron multiplicity sorting based on measured neutron energies. Partial reaction cross sections σeval(g,in) = Fitheor x σexp(g,xn) for 52Cr and 68Zn, were evaluated using the experimental yield cross sections σexp(g,xn) = σexp(g,1n) + 2σexp(g,2n) + 3σexp(g,3n) and the ratios Fitheor = σtheor(g,in)/σtheor(g,xn) calculated for i = 1, 2, 3 in Combined photonuclear reaction model (CPNRM). The published cross sections σ(g,sn) = σ(g,1n) + σ(g,2n) and σ(g,1n) for 52Cr and σ(g,xn) for 68Zn obtained using beams of bremsstrahlung were used. It was found that cross-section 52Cr(g,1n)51Cr obtained before using the method of introducing statistical theory corrections to the yield cross-section σexp(g,xn) is significantly underestimated in comparison with evaluated one and therefore do not meet physical criteria. The reason is that at photon energies where reactions (g,1n) and (g,2n) compete with each other, the statistical evaporation model became less accurate because processes of the pre-equilibrium decay of a composite system become more important. The CPNRM used in the evaluation method is free from those shortcomings. New data for cross sections of reactions 52Cr(g, 1n)51Cr, 52Cr(g, 2n)50Cr, 68Zn(g, 1n)67Zn and 68Zn(g, 2n)66Zn were evaluated in accordance with reliability criteria.