The specific features of photoneutron reactions on 58Ni

The reliability of experimental data on partial photoneutron reaction cross sections (gamma, 1n) and (gamma, 2n) for Ni-58 obtained in experiments carried out using beams of both bremsstrahlung and quasimonoenergetic annihilation photons were analyzed using the objective physical criteria. It was found out that data obtained using bremsstrahlung are not reliable definitely. At the same time, it was shown that there are serious doubts in reliability of data obtained using quasimonoenergetic photons and the method of photoneutron multiplicity sorting. New reliable cross sections of partial and total photoneutron reactions were obtained using the experimental-theoretical method of evaluation basing on the joint using of the experimental neutron yield cross-section which is rather independent of neutron multiplicity and the results of calculations in the Combined PhotoNucleon Reaction Model (CPNRM). The significant disagreements between the new reliable evaluated cross sections and the experimental ones for both partial reactions (gamma, 1n) and (gamma, 2n) were analyzed in detail. It was shown that the main reason of disagreements is that experimental cross-section of (gamma, 1n1p) reaction was unreliably (erroneously) interpreted as that of (gamma, 2n) reaction.