Shape comparison of physical spectra: Application to Mössbauer spectra of silicate glasses

Massiot, Dominique

doi:10.1016/0022-3093(85)90038-9

Cited by 5 publications

(2 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This problem of fitting the spectra of glasses is enhanced compared with crystalline spectra because of the distributions of hyperfme fields for both ferrous and ferric iron. The inference that there is a coordination transformation of ferric iron as a function of Fe'+/E;Fe at fixed temperature, pressure and bulk composition is consistent with other studies of synthetic glasses (MASSIOT, 1985;SPIERING and SHFERT, 1985).…”

Section: Structural Assignments Offerrous and Ferric Ironsupporting

confidence: 89%

The effect of oxidation state on the viscosity of melts in the system Na2O-FeO-Fe2O3-SiO2

Dingwell

Virgo

1987

Geochimica et Cosmochimica Acta

142

View full text Add to dashboard Cite

Abstract-The viscosities of two melts in the system Na2o-Feo_Fe203s~ have been measured as a function of oxidation state. The experiments were conducted by concentric-cylinder viscometry, on melts equilibrated with CO/COr gas mixtures in a vertical tube, gas-mixing furnace. Viscosity determinations were made during stepwise reduction and oxidation of the melts. "Fe Miissbauer spectra were obtained on quenched melt samples recovered during the viscometty experiments. In addition, a series of loop fusion experiments were performed at calibratedfOz values in order to relate viscosity determinations directly tojO*.The viscosities of acmite and NS4F40 (Na-tich and Si-poor relative to acmite) melts decrease with mduction of Fe in the melts, as nonlinear functions of F$+/ZFe, yielding a region of viscosity invariance at moderate to low values of Fes+/ZFe (~0.4). The 57Fe M&batter spectra of quenched melts as a fimction of Fe3"/ZFe ind&ate the presence of one (ne~ork-rn~~ng) ferrous species and two ferric species with ferric iron acting dominantly as a network-former in oxidixed melts and dominantly as a network-modifier in reduced melts.The presence of two ferric iron species produces a minimum in the degree of polymerization of the melt at intermediate values of Fe'+/ZFe: the region of viscosity invariance corresponds to this minimum. If viscosity is positively correlated with polymeriration for all values of Fe3*/2Fe then the viscosity of very reduced melts will increase with reduction, as the melt polymerizes.The effect of oxidation state on viscosity is large and illustrates that ferric iron should be considered as a separate component in calculation schemes for estimating the viscosity of natural magmas. I~ODU~ONA CHANGE OF the chemical potential of oxygen during igneous petrogenesis will, in general, result in a change in the oxidation state of the igneous melt expressed as the ferric-ferrous ratio. Accordingly, geochemists have long recognized the usefulness of ferric-ferrous ratios of minerals and melts for inferring redox trends in igneous rock series.More recently, the intluence of the ferric-ferrous ratio on the physical properties of silicate melts has received attention (e.g. viscosity, CUKIERMAN and UHLMANN, 1974; density, MO et al., 1982). Viscosity is a physical property of silicate melts that is central to the discussion of mass transfer within or between phases. Processes that involve mass transfer are, in turn, the fundamental mechanisms of igneous differentiation.Despite the observation that iron is a major constituent of igneous melts, current info~ation regarding the effect of redox equilibria on the viscosity of ironbearing melts is scarce. This scarcity of information was noted by BOTTINGA and WEILL (1972). These authors were forced to neglect the possible effects of oxidation state on viscosity in the development of their now widely used calculation scheme for estimating the viscosity of igneous melts. limited the precision of some of these data and complicate comparison and gene~~on of the res...

show abstract

Section: Structural Assignments Offerrous and Ferric Ironsupporting

confidence: 89%

The effect of oxidation state on the viscosity of melts in the system Na2O-FeO-Fe2O3-SiO2

Dingwell

Virgo

1987

Geochimica et Cosmochimica Acta

142

View full text Add to dashboard Cite

show abstract

“…The adjustment of the fit of the experimental spectra to the model function is done with an interactive multiple least square fitting program developed by Massiot [ 29 ], minimizing the residual distance normalized to the number of data points (standard deviation SD) according to

where n is the number of data points, P ′( λ i) is the number of counts at channel i and P ′( λ i) is the value of the model function at that point i. The method utilizes an iterative non-linear least-squares fitting process starting from an initial estimated solution.…”

Section: Applications Of Least-square Fitting Techniques To Wds Spmentioning

confidence: 99%

Decomposition of wavelength dispersive x-ray spectra

Rémond¹,

Myklebust²,

Fialin³

et al. 2002

J. Res. Natl. Inst. Stand. Technol.

View full text Add to dashboard Cite

Line shapes of atomic lines and soft x-ray emission bands measured with a wavelength dispersive spectrometer (WDS) with the Electron Probe Micro Analyzer (EPMA) are reviewed. Least square fitting to pseudo-Voigt profiles of the digitally measured spectra are used to account for the presence of non-diagram features (high and low energy satellites) and instrumental induced distortions. The effect of line width and relative intensities on the quality of fits is illustrated. Spectral distortions resulting from the presence of absorption edges within the analyzed wavelength region are illustrated for the case of FeLα,β emission bands for pure Fe and iron oxides. For quantitative analysis, an analytical approach is presented where the measured soft x-ray emission bands are corrected for self absorption before extracting the intensities from the experimental data.

show abstract