Interpretation of measurements of π⁰-meson photoproduction partial cross sections on a⁶Li nucleus with O⁺ level excitation

The anomalously large measured values of the cross section of the reaction γ+⁶Li → Π⁰ +⁶Li^* (3.56 MeV), which were obtained in two different laboratories, 260-450 MeV γ-rays, are discussed. It is shown that the disagreement between theory and experiment is due to the background reaction γ +⁷Li → Π⁰ + n +⁶Li^* (3.56 MeV), which became possible as a result of the poor isotropic purity of the target. This background reaction is discussed with respect to obtaining data on Π⁰-meson photoproduction on neutrons.