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[en] A comparative analysis of the copper and iron ions bonds exchange energies was conducted for various variants of orderings and distributions of iron ions among crystallographic positions in ludwigite Cu2FeBO5. Analysis showed that the exchange bonds of iron ions play a key role in the formation of magnetic order. The magnetic ordering strongly depends on the distribution of iron ions among the positions. In the case when the Fe3+ is in the same position as in Fe3BO5, the most favorable magnetic structure is similar to the magnetic structure of ludwigite Fe3BO5. In other cases, the type of magnetic ordering is different.
[en] Investigated bay gamma-resonance spectroscopy (GRS) chelation of iron ions with sinthetic LDOPA-melanin and melanin isolated from the beans black grapes, hedera helix and sambucus nigra. It is found that melanin effectively chelate iron ions in both its two and in the tri valent state. The main part of the coordinated ions Fe''3+ ions are part of polynuclear (n≥2) clusters and with fast relaxation spin-spin iteraction gives paramaqnetic dublet GR-spectra. The presence of magnetic relaxation spectra indicates that part of the lokal points in melanin separated. The value of the parameters GR-spectra of the samples are characteristic of high-spin complex ions Fe''2+ and Fe''3+ with octahedrial ligand environment. It is expected that the ability of vegetable melanins effectiveli bing prooksidant Fe''2+ ions may be one of the possible mechanisms of their antioksidant and radioprotective properties.
[en] The currently available data for electron impact excitation of the iron ions, Fe I-Fe VIII, are assessed and listed according to their sources. Methods and approximations employed and the transitions considered are also given. 21 refs., 1 fig., 3 tabs
[en] Two rhodamine-based sensors RDI-1, RDI-2 was designed and synthesized by incorporation of the rhodamine 6G fluorophore and 2-formyl imidazole as the recognizing unit via the imine linkages. RDI-1, RDI-2 exhibits very high selectivity and an excellent sensitivity towards Fe(III) ions in aqueous buffer solution on compared with other probes. The color change from colorless to pink and turn-on fluorescence after binding with iron (III) was observed. Based on jobs plot and ESI-MS studies, the 1:1 binding mode was proposed. Live cell imaging experiments with each probe showed that these probes widely applicable to detect Fe3+ in living cells. -- Highlights: • Two rhodamine based probes was synthesized and used to recognize iron (III). • The chemosensors can be applied to detect iron(III) ions by color and turn-on fluorescent changes. • The very low detection limit was reported. • The applicability of these probes for live cell fluorescence imaging was studied
[en] Fluorescent organic molecules that respond to changes in the Fe2+ concentration with selectivity to other abundant di-valent metal ions will offer the ability to understand the dynamic fluctuations of the Fe2+ ion in interesting media. The use of 6-Br-ppmbi, derived from 2-pyridin-2-yl-benzimidazole, for metal ion-selective fluorescence recognition was investigated. Screening of the main group and transition metal ions showed exclusive selectivity for Fe2+ ions even in the presence of competing metal ions. In addition, the requirement for low concentrations of probe molecules to detect certain amounts of Fe2+ ions make this sensor unique compared to previously reported Fe2+ ion sensors
[en] We develop the methodology of quadrupole splitting distribution (QSD) analysis by evaluating the influences of absorber thickness, absorber texture, and the asumed Lorentzian width on the extracted QSD. We then present the first study to describe the Moessbauer spectra of members of a mineral family in terms of QSDs. The Fe2+ QSD and its characteristics (average QS, peak QS, skewness, and standard deviation) show gradual trends with changing Fe/(Fe+Mg) in a synthetic Al-deficient phlogopite-annite series. Al-deficient natural samples of phlogopite and annite show similar behaviour. The Fe2+ QSDs can be interpreted as population distribuitions of local distortion environments (LDEs) and, as such, contain much information that will become more accessible as theoretical calculations linking particular LDEs to corresponding QS values are developed. (orig.)
[en] Electron impact collisions with ground-state ions in a low-density plasma may cause ionization either by direct ejection of an electron from the ion, or by excitation of an inner-subshell electron to an autoionizing level. We investigate the importance of the indirect process in sodium-like Fe XVI by means of detailed calculations of excitation cross sections and of branching ratios for autoionization versus radiative decay; the estimated accuracy is about 20%. We find that radiative decay reduces the autoionization rate (at kT=300--500 eV) to only about 52% of the excitation rate; even so, the indirect ionization rate is about 1.4--1.6 times the direct ionization rate in this temperature range. The relative importance of indirect to direct ionization is approximately as great for Na-like Mo XXXII as for Fe XVI, but should be much smaller for most nonalkali-like ions except Cu-like, Zn-like, and perhaps Ga-like ions