Mössbauer Isomer Shifts

Shenoy, G. K.; Wagner, F. E.; Wickman, H. H.

doi:10.1063/1.2995496

Cited by 112 publications

(72 citation statements)

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“…The weighted average isomer shift, <δ>, is typical of iron(III) (Shenoy et al, 1978) and spectral analysis indicates that at least 98 % of the iron in the mineral crust must be present as iron(III); two percent by spectral area is the approximate detection limit for the presence of any iron(II). The average hyperfine parameters observed at 295 and 4.2 K are typical (Murad et al, 1987) of two-line ferrihydrite.…”

Section: Iron Oxides Identified By Mössbauer Spectroscopymentioning

confidence: 99%

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata

Corbari¹,

Cambon-Bonavita

Long

et al. 2008

Biogeosciences

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Abstract. The Rimicaris exoculata shrimp is considered as a primary consumer that dominates the fauna of most Mid-Atlantic Ridge (MAR) hydrothermal ecosystems. These shrimps harbour in their gill chambers an important ectosymbiotic community of chemoautotrophic bacteria associated with iron oxide deposits. The structure and elemental composition of the mineral concretions associated with these bacteria have been investigated by using LM, ESEM, TEM STEM and EDX microanalyses. The nature of the iron oxides in shrimps obtained from the Rainbow vent field has also been determined by Mössbauer spectroscopy. This multidisciplinary approach has revealed that the three layers of mineral crust in the Rimicaris exoculata shrimps consist of large concretions formed by aggregated nanoparticles of two-line ferrihydrite and include other minor elements as Si, Ca, Mg, S and P, probably present as silicates cations, sulphates or phosphates respectively that may contribute to stabilise the ferrihydrite form of iron oxides. TEM-observations on the bacteria have revealed their close interactions with these minerals. Abiotic and biotic precipitation could occur within the gill chamber of Rimicaris exoculata, suggesting the biologically-mediated formation of the iron oxide deposits. The difference of the bacterial density in the threemineral crust layers could be correlated to the importance of the iron oxide concretions and suggest that the first mineral particles precipitates on the lower layer which could be considered as the most likely location of iron-oxidizing bacteria.

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Section: Iron Oxides Identified By Mössbauer Spectroscopymentioning

confidence: 99%

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata

Corbari¹,

Cambon-Bonavita

Long

et al. 2008

Biogeosciences

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“…The calculation of the Mössbauer isomer shift via calculated contact densities requires a number of approximations [44]. In the traditional approach [45][46][47], the energy shift associated with going from a point nucleus to a nucleus of finite size is expressed in terms of perturbation theory and evaluated separately for the ground and excited nuclear state.…”

Section: Validity Of the Contact Density Approximationmentioning

confidence: 99%

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Knecht

Fux

Meer³

et al. 2011

Theor Chem Acc

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The electrostatic contribution to the Mössbauer isomer shift of mercury for the series HgF n (n = 1, 2, 4) with respect to the neutral atom has been investigated in the framework of four-and two-component relativistic theory. Replacing the integration of the electron density over the nuclear volume by the contact density (that is, the electron density at the nucleus) leads to a 10% overestimation of the isomer shift. The systematic nature of this error suggests that it can be incorporated into a correction factor, thus justifying the use of the contact density for the calculation of the Mössbauer isomer shift. The performance of a large selection of density functionals for the calculation of contact densities has been assessed by comparing with finite-field four-component relativistic coupled-cluster with single and double and perturbative triple excitations [CCSD(T)] calculations. For the absolute contact density of the mercury atom, the Density Functional Theory (DFT) calculations are in error by about 0.5%, a result that must be judged against the observation that the change in contact density along the series HgF n (n = 1, 2, 4), relevant for the isomer shift, is on the order of 50 ppm with respect to absolute densities. Contrary to previous studies of the 57 Fe isomer shift (F Neese, Inorg Chim Acta 332:181, 2002), for mercury, DFT is not able to reproduce the trends in the isomer shift provided by reference data, in our case CCSD(T) calculations, notably the non-monotonous decrease in the contact density along the series HgF n (n = 1, 2, 4). Projection analysis shows the expected reduction of the 6s 1/2 population at the mercury center with an increasing number of ligands, but also brings into light an opposing effect, namely the increasing polarization of the 6s 1/2 orbital due to increasing effective charge of the mercury atom, which explains the nonmonotonous behavior of the contact density along the series. The same analysis shows increasing covalent contributions to bonding along the series with the effective charge of the mercury atom reaching a maximum of around ?2 for HgF 4 at the DFT level, far from the formal charge ?4 suggested by the oxidation state of this recently observed species. Whereas the geometries for the linear HgF 2 and square-planar HgF 4 molecules were taken from previous computational studies, we optimized the equilibrium distance of HgF at the four-component Fock-space CCSD/aug-cc-pVQZ level, giving spectroscopic constants r e = 2.007 Å and x e = 513.5 cm -1 .Dedicated to Professor Pekka Pyykkö on the occasion of his 70th birthday and published as part of the Pyykkö Festschrift Issue.Electronic supplementary material The online version of this article

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“…Burger [73] and Bancroft et al [74] tried to correlate this by partial values of d and D. There have been attempts [75,76,87] to correlate d and D to obtain additional information. Burns [96][97][98] tried to relate different crystalline structures graphically using Mö ssbauer parameters of d and D and correlated these parameters with various bonds length-related parameters as mean metaloxygen distance of a coordination site, and the volume per oxygen in a unit cell and polyhedral volume. But this method failed in several cases to delimit d ranges for Fe ‫ם2‬ and Fe ‫ם3‬ ions in silicates.…”

Section: Identification Of Crystalline Structuresmentioning

confidence: 99%

Automation in M�ssbauer spectroscopy data analysis

Souza

1999

Lab. Robotics Autom.

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Mössbauer Isomer Shifts

Cited by 112 publications

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Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp <i>Rimicaris exoculata</i>

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp <i>Rimicaris exoculata</i>

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Automation in M�ssbauer spectroscopy data analysis

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Mössbauer Isomer Shifts

Cited by 112 publications

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Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp &lt;i&gt;Rimicaris exoculata&lt;/i&gt;

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp &lt;i&gt;Rimicaris exoculata&lt;/i&gt;

Mössbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

Automation in M�ssbauer spectroscopy data analysis

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Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp <i>Rimicaris exoculata</i>

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp <i>Rimicaris exoculata</i>