Measurement of recoil-free fractions in studies of the Mössbauer effect

Housley, R. M.; Erickson, N. E.; Dash, J. G.

doi:10.1016/0029-554x(64)90132-6

Cited by 108 publications

(24 citation statements)

References 9 publications

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“…1 and 2 are presented in Table 1. The spectral areas have been corrected for the nonresonant background count rate according to the procedure described by Housley et al (7), the variation in these corrections not exceeding 1% from spectrum to spectrum. The spectra of Fig.…”

Section: Resultsmentioning

confidence: 99%

Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy

Boudart

Dumesic²,

Topsøe³

1977

Proc. Natl. Acad. Sci. U.S.A.

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The superparamagnetic behavior of very small particles of metallic iron (ca 1.5 nm), with about half of their atoms at the surface, is changed reversibly by adsorption and desorption of hydrogen below the superparamagnetic transition EXPERIMENTALThe Mossbauer spectrometer, the cells, and the gas handling systems have been described elsewhere (1, 4). The essential feature is the capability of collecting Mossbauer spectra with the sample in flowing palladium-diffused hydrogen or purified helium between 300 and 800 K within ±1 K. Helium was used as a convenient, noncontaminating alternative to high vacuum.The magnetic susceptibility data were obtained by the Faraday method, with an apparatus described elsewhere (5). In brief, a water-cooled electromagnet provided variable fields up to 300 kA-m-(1 G = 103 A-m-') and field gradients up to 3 MA-m-2 (1 Oe = 79.6 A-m-2). The multipurpose gas-handling vacuum system that allowed gassing with H2 or He and evacuation to O-4 Pa between 77 and 720 K. For purification, the H2 was passed through a Deoxo unit, and the He was passed through copper turnings at 500 K. Both gases were subsequently passed through separate molecular sieve (Linde 13X) traps at 77 K. The samples, prepared and characterized as described elsewhere (1), were 1%, 3%, and 8% iron (wt/wt) supported on magnesium oxide with metallic iron dispersions of 0.5, 0.2, and 0.1, respectively (dispersion, D, of the metal is defined as the fraction of the iron atoms that are surface atoms). The corresponding surface average particle sizes were 1.5, 4.0, and 8.0 nm, respectively. The fraction of the iron present as 57Fe for these three samples was 0.26, 0.32, and 0.022, respectively. For convenience these three samples will be referred to as Fe(D = 0.5), Fe(D = 0.2), and Fe(D = 0.1), respectively. RESULTSMossbauer Spectroscopy. A known quantity of the sample Fe(D = 0.5) was reduced in flowing H2 according to the previously described reduction schedule (1). M6ssbauer spectra were then collected in flowing H2 at 298 and 683 K (Fig. 1) and in flowing He at 683 K (Fig. 2). The qualitative features of these spectra reveal two different states of iron in the reduced sample: metallic iron giving rise to the magnetically split spectral component, and Fe2+ in MgO which is responsible for the central spectral doublet (1). In the present study, it is the metallic iron species that is of interest. It represents about half of the total iron in all the reduced samples.The particle size dependence on the above effect of the gaseous atmosphere over the sample was studied by obtaining spectra of sample Fe(D = 0.2). This sample was reduced, and a spectrum was taken at 390 K in flowing H2 with the velocity offset method, which allows the scanning of the two metallic iron peaks that are located the furthest from the zero of velocity (6). This method provides greater sensitivity to change in the metallic iron spectrum than that possible with the constant acceleration mode used to collect the data of Figs. 1 and 2. The sample was t...

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Section: Resultsmentioning

confidence: 99%

Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy

Boudart

Dumesic²,

Topsøe³

1977

Proc. Natl. Acad. Sci. U.S.A.

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“…I n order to measure O(-2) and O(-1)) the area A under the absorption dip at various temperatures is estimated by obtaining a velocity spectrum of the absorption dip and integrating over the line-shape by a method given by Housley et al [7]. The integrated absorption area A is obtained by integrating the transmitted intensity as the source is moved to scan the velocity range &V and then calculating from a linear plot of the average intensity I ( 8 ) …”

Section: Methodsmentioning

confidence: 99%

An Estimation of Force Constant Change of Mössbauer ¹¹⁹Sn Impurity Nuclei in Palladium Host

Puri

Gupta

1975

Physica Status Solidi (b)

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Precision measurements are made of the second order Doppler shift and absorption areas of the Mossbauer line of ll9Sn, present as a dilute impurity in palladium lattice, over a range from liquid helium temperature to about 750 O K . The weighted mean temperatures have been determined from the moments w ( -2 ) , w ( -l), w ( + l), and w( + 2 ) of the phonon frequency distribution in the palladium lattice as seen by the Mossbauer l19Sn impurity atoms. Assuming a Debye spectrum, ratios of the impurity-host t o host-host spring force constants have been estimated from the characteristic temperatures on the basis of Mannheim's model of nearest neighbour central forces. The Sn-Pd force constant has been found weaker than the equivalent Pd-Pd force constant indicating the presence of resonance band modes without any evidence of localised impurity modes.Es werden Prlzisionsmessungen der Doppler-Verschiebung zweiter Ordnung und der Absorptionsflachen der MoDbauerlinie von ll9Sn, das als verdunnte Storstelle im Palladiumgitter vorliegt, im weiten Temperaturbereich vom flussigen Helium bis etwa 750 O K durchgefuhrt. Die gewichteten mittleren Temperaturen werden aus den Momenten w ( -2 ) , w ( -l), w ( + l ) und w ( + 2 ) der Verteilung der Phononenfrequenzen im Palladiumgitter bestimmt, die auf die 119Sn-Mol3bauerstorstellen einwirken. Unter der Annahme eines DebyeSpektrums werden die Verhaltnisse der Storstellen-Wirtsgitter-zu den Wirtsgitter-Wirtsgitter-Federkonstanten aus den charakteristischen Temperaturen auf der Basis des Modells yon Mannheim fur die Zentralkrafte der iiachsten Nachbarn berechnet. Es wird gefunden, daD die Sn-Pd-Kraftkonstante schwacher als die aquivalente Pd-Pd-Kraftkonstante ist, was die Anwesenheit von Resonanzmoden anzeigt, ohne irgendeinen Hinweis auf lokalisierte Storstellenmoden.

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“…Coarser soil-sample fractions were further ground to obtain better homogeneity and to improve the reliability of area results (Saragovi and Mijovilovich, 1997). High counting rates (3-5 x 106 counts/channel) were used, and a background correction was measured (Housley et al, 1964). Similar experimental conditions were maintained for all measurements.…”

Section: Miissbauer Spectroscopymentioning

confidence: 99%

Iron-Oxide Mineralogy of a Mollisol from Argentina: A Study By Selective-Dissolution Techniques, X-Ray Diffraction, and Mössbauer Spectroscopy

Acebal

Mijovilovich

Rueda

et al. 2000

Clays and clay miner.

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Abstract--Selective-dissolution techniques by ammonium oxalate (OX), dithionite-citrate-bicarbonate (DCB), and dithionite-ethylenediaminetetraacetic acid (D-EDTA), and X ray diffraction and M6ssbauer spectroscopy were used to identify and characterize iron oxides and oxyhydroxides in the <2-mm, <50-p,m, and <2-p~m size fractions of a Mollisol from Bahia Blanca, Argentina. Iron compounds are present at low concentrations in mixtures with quartz, Na-rich feldspar, illite, interstratified illite-montmorillonite, and traces of kaolinite. Total Fe and AI content increases as soil particle size decreases, from 4.3 and 13.3 wt. % in the <2-mm size fraction to 8.5 and 22.8 wt. % in the clay fraction (<2 Ixm), respectively. No more than 25-30% of the total Fe is associated with the crystalline and the amorphous Fe oxides. Weakly ferromagnetic hematite and goethite were identified in the different fractions. These phases have small particle sizes and/or low crystallinity. They may also have A1 for Fe substitutions. Crystalline magnetite or maghemite is rare. These Fe-rich phases are probably coating coarser particles.The efficiency of Fe removal is highest for the D-EDTA treatment and least efficient for the OX method, for all fractions. The opposite is true for A1 removal. Poorly crystalline hematite and goethite, which are soluble in oxalate, are only present in the coarser fractions. Poorly crystalline and crystalline hematite and goethite, which are soluble in DCB and EDTA, are present in coarser fractions, but do not occur in the clay fraction. DCB treatment probably dissolves A1 in the 2:1 type phyllosilicates occurring in this soil, whereas D-EDTA dissolves Fe in the hydroxy interlayers of the srnectite minerals or in the silicate phases.

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Measurement of recoil-free fractions in studies of the Mössbauer effect

Cited by 108 publications

References 9 publications

Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy

Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy

An Estimation of Force Constant Change of Mössbauer ¹¹⁹Sn Impurity Nuclei in Palladium Host

Iron-Oxide Mineralogy of a Mollisol from Argentina: A Study By Selective-Dissolution Techniques, X-Ray Diffraction, and Mössbauer Spectroscopy

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Measurement of recoil-free fractions in studies of the Mössbauer effect

Cited by 108 publications

References 9 publications

Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy

Surface, catalytic, and magnetic properties of small iron particles: The effect of chemisorption of hydrogen on magnetic anisotropy

An Estimation of Force Constant Change of Mössbauer 119Sn Impurity Nuclei in Palladium Host

Iron-Oxide Mineralogy of a Mollisol from Argentina: A Study By Selective-Dissolution Techniques, X-Ray Diffraction, and Mössbauer Spectroscopy

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An Estimation of Force Constant Change of Mössbauer ¹¹⁹Sn Impurity Nuclei in Palladium Host