Isomer shift in Mössbauer spectra of iron compounds in different oxidation states in the octahedral or tetrahedral oxygen environment

Ranges and average of the isomer shift for iron atoms in different oxidation states in (violet) tetrahedral and (red) octahedral interstices of oxo compounds at room temperature, and approximation of average straight lines for (solid line) room temperature and (dash line) liquid_nitrogen temperature (data are not presented) according to published dataMössbauer study of oxo derivatives of iron in the Fe2O3-Na2O2 system. Pankratov D.A. //Inorganic Materials, 2014. V. 50. № 1. P. 82-89

As a rule, interpretation of poorly resolved Mössbauer spectra is an intricate, multiparametric problem. A measured spectrum is fitted using a particular model based on available information about the composition, structure, and properties of the sample. A criterion for whether the spectrum has been adequately decomposed into components is the agreement between the obtained parameters and expected ones for realistic physical and chemical models. A criterion for sufficiency is provided by statistical parameters of the deviation of results of the proposed model from experimental data. Clearly, a larger number of subspectra in a model and a smaller number of constraints for their components ensure better fitting quality. In some cases, when the iron atoms in a sample have an inhomogeneous environment and parameters of subspectra vary continuously in some range, or spectra contain overlapping components (resonance lines), a model-free description of spectra is used, instead of models. However, a model-free description of spectra also requires an adequate initial hypothesis as to the properties of the substance to be studied. In some cases, even with well-resolved spectra, an incorrect initial hypothesis may entail inadequate interpretation of experimental data.


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Возможности криогенной авторадиографии

Типичные авторадиограммы, полученные при различных условиях экспонирования (отмечены области, отвечающие загрязнению обоймы источника)

Возможности криогенной авторадиографии. Панкратов Д.А., Коробков В.И. //Журнал аналитической химии. 2014. Т. 69. № 7. С. 700–706Search the full text below. Ищи полный текст ниже.

Изучены фотографические свойства ядерного фотодетектора BioMax MR Film фирмы KODAK при температуре жидкого азота. Характеристические кривые, полученные при комнатной и криотемпературах, свидетельствуют о сохранении фотодетектором физических и фотографических свойств, что расширяет области применения его вплоть до исследования глубоко замороженных образцов. Получены данные об увеличении чувствительности замороженного до криогенных температур фотоматериала для малых экспозиций.


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Platinum(IV) Superoxo Complexes

Evolution of the VIS-spectra of the blue solutions in time

Platinum(IV) Superoxo Complexes. Kiselev Yu.M., Pankratov D.A., Ezerskaya N.A., Kiseleva I.N., Shundrin L.A., Popovich M.P. //Russian Journal of Inorganic Chemistry. 1994. V.39. №8. P. 1278-1283Search the full text below. Ищи полный текст ниже.

The products of reaction of platinum(IV) hydroxo complexes with ozone in alkaline solutions were studied using various physicochemical methods: electronic spectroscopy, electron spin resonance, and cyclic voltammetry. The arguments presented suggest that the blue solutions obtained contain superoxo Pt(IV) complexes.

One of the most efficient ways to stabilize higher oxidation states in the transition elements is complex formation in aqueous-alkaline media. In this case, hydroxyl ions offer advantages over other ligands and produce a stronger decrease in E° of a redox system than other, rather weakly polarizable ligands, which form complex ions in acid and neutral media. This circum stance is the one favoring stabilization of the highest oxidation states in neptunium, plutonium, americium(VII), and iron(VIII).


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