ИСТИНА

In cases for many (~50) nuclei from 51V to 209Bi the experimental data on photoneutron partial reactions (g,1n), (g,2n), (g,3n) cross sections directly obtained using beams of quasimonoenergetic annihilation photons do not satisfy objective physical criteria of data reliability. The reasons are systematic uncertainties of experimental photoneutron multiplicity sorting method basing on partial reactions separation via measurement of neutron energies. Therefore, the experimental-theoretical method for partial reaction cross-section evaluation basing on physical criteria was used for analysis of reliability of data obtained using quite different method on the beams of bremsstrahlung. Partial reaction cross sections are separated and determined in such kind experiment using statistical theory corrections to the neutron yield cross section σ(g,xn) = σ(g,1n)+2σ(g,2n)+3σ(g,3n)+… measured at first. Experimental cross sections of the reactions (g,1n) and (g,2n) are definitely unreliable in the cases of 51V, 52Cr, 59Co, but enough reliable in the case of 90Zr. The reason is that the role of two-nucleon reaction (g,1n1p) was not taken into account, though this reaction competes with also two-nucleon reaction (g,2n). It was shown via the results of calculation in the frame of the Combined photonuclear reaction model that energy positions and amplitudes of cross sections of (g,1n1p) and (g,2n) reactions are very close to each other in the cases of 51V, 52Cr, 59Co, but in the case of 90Zr the value of (g,1n1p) reaction cross section is very small and could be negligible. This conclusion is analogous to that of the preliminary investigation of the cases of 127I, 165Ho, 181Ta. It means that in the cases of relatively light nuclei 51V, 52Cr, 59Co, as well as 58,60Ni the reaction (g,1n1p) plays important role in nucleus photodisintegration but its contribution is not correctly described by statistical theory corrections.