Ferric oxide, Mossbauer spectra

Hobson and Campbell reported that the Mossbauer spectrum of a sample of iron oxide on silica gel, which has been calcined at 500°C for 16 hr, showed (65) a small chemical isomer shift of 0.29 mm see -1 and an unusually large quadrupole splitting of 1.87 mm sec-1. This splitting was noted to be larger than 1.60 mm sec-1 calculated by Flinn et al. (17) for a ferric ion in an octahedral environment with 1 oxygen atom missing but less than 2.26 mm sec -1 calculated for the... 

Cleavage of the first species to the transient ferryl complex and a ferric hydroxo monomeric complex can explain the near 50% yield of the ferryl compound. The ferric monomer subsequently dimerizes to the paramagnetic dimer, 32, responsible for the 65% of the Mossbauer signal. The dimer formed after the oxidation is proposed to be similar to the starting material, based on comparisons of its Mossbauer spectrum with that of 31. 

Figure 3. Room temperature Mossbauer spectra of coal samples from the Pratt seam in Alabama (top) and from an anthracite deposit in Rhode Island (bottom). In the top spectrum, peaks indicated arise from iron in the common coal minerals pyrite (P), clays (C), siderite (S), and jarosite (J), In the bottom spectrum, peaks indicated arise from iron in clays (C), and in the rare coal minerals, ankerite (A), iron metal (I), and ferric oxide (H),...

Nature s strategies to store two oxidizing equivalents in heme proteins. The inset shows a Mossbauer spectrum of a bis-Fe(IV) intermediate in MauG [7], The hashed marks are the experimental data of diferric MauG reacting with 1 equiv of H2O2 for 45 s. The noisy line indicates the contribution of ferric heme ( 34% of total Fe). The simulated smooth solid line represents two Fe(IV) species. See the text for details. 

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