Skobeltsyn Institute of Nuclear Physics
Lomonosov Moscow State University

The reasons of well-known systematic discrepancies of results of photonuclear experiments carried out using
beams of quasimonoenergetic photons from annihilating in flight of relativistic positrons and that of bremsstrahlung
have been investigated in details. The complete photonuclear reaction cross section information obtained on all steps of
quasimonoenergetic photons experiment reaction cross section data obtaining traditional subtraction procedure has been
studied. On the base of this information comparison with bremsstrahlung experiments data and theoretical calculations it
has been obtained that using of subtraction procedure mentioned leads to the significant missing of the information on
the studied reaction cross section structure. It has been shown that for complex (asymmetric line with large low energy
background) shape of real photon spectrum (experiment apparatus function) the subtraction procedure decreases in
several times the really obtained energy resolution in comparison with its estimation based on the calculated width of
annihilation line in the spectrum of photons produced by annihilation positrons.