ИСТИНА

According to the existing concept, an increase in electron density on 57Fe nucleus must lead to a decrease in Mӧssbauer isomer shift (IS). The rise of oxi- dation state of iron (escape of electrons from the valence shell) usually leads to the decrease in IS, which is explained by the shielding effects. We suggest applying the approach of the valence shell hybridization to explain the regularities of the IS change [1]. It is easy to show that two electrons on 4s-orbital create the electron density at the iron nucleus, which is equivalent to the density created by the full set of fully filled 4s4pn 3dm-hybridized orbitals: !!(0) ! =