Mössbauer study of iron in atmospheric air

Abstract

Use of the Mössbauer effect has been made for studying iron in atmospheric air. The experiments were performed by observing the absorption of 14.4 keV gamma rays from ⁵⁷Co by samples consisting of filters through which atmospheric air was pumped. Using the “area method” usually applied in calculations of the recoilless raction (f-factor) the content of natural iron per cubic meter of atmospheric air was found to be 1.4 μg/m³. The measurements were carried out at room and liquid nitrogen temperatures. The room temperature spectra show two absorption lines due to quadrupole splitting; the low temperature spectrum shows a central unresolved doublet and, besides it, six lines due to magnetic hyperfine splitting. From the shapes of the Mössbauer spectra obtained it was inferred that iron appears in the Fe₂O₃ compound in the form of ultrafine particles (∼ 100 Å) in the superparamagnetic state.