EXAFS: New Horizons in Structure Determinations

Eisenberger, P.; Kincaid, B. M.

doi:10.1126/science.663627

Cited by 165 publications

(61 citation statements)

References 45 publications

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“…EXAFS has been studied extensively in the past [30,31,32]. EXELFS, on the other hand, has received very limited attention because poor counting statistics and the possibility of beam-damage from prolonged irradiation have discouraged the development of this technique to its full potential.…”

Section: Exafs and Exelfsmentioning

confidence: 99%

“…The (Pd-Ni) 80 P 20 BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni) 80 P 20 BMGs can be explained in terms of the stability of Pd 60 Ni 20 P 20 and Pd 30 Ni 50 P 20 , glasses at the end of BMG formation.…”

mentioning

confidence: 99%

“…Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd 40 Ni 40 P 20 is further described by a weighted average of those of Pd 30 Ni 50 P 20 and Pd 60 Ni 20 P 20 . Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms.…”

mentioning

confidence: 99%

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Stability of bulk metallic glass structure

Jain¹,

Williams²

2003

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Section: Exafs and Exelfsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Stability of bulk metallic glass structure

Jain¹,

Williams²

2003

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“…This consists of the intensity oscillations that mainly occur on the jump top, known as EXAFS oscillations. 9 In order to measure a jump correctly, a linear adjustment of the experimental points in the vicinity of the absorption edge was made over the top ( Ä q i ) and over the background ( > q i ) of the jump, respectively. Such straight lines compensate for the EXAFS oscillations.…”

Section: Corrections Of the Jump Measurementmentioning

confidence: 99%

Selective excitation and integral counting of x‐ray fluorescence (SEICXRF)

Figueroa

2003

X-Ray Spectrometry

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INTRODUCTIONThe conventional x-ray fluorescence (XRF) spectrometer is based on the ionization of the atoms present in the sample using, as excitation source, either photons with several discrete energies (from radioisotope sources) or with an energy spectral distribution (from an x-ray tube or synchrotron radiation). An alternative XRF method is presented here. In this case, the atoms of the elements present in the sample are selectively excited using, for that purpose, a beam of monochromatic radiation whose energy is tuned in a sequential way to scan the desired range of energies. All the photons emerging from the sample (scattered photons and characteristic fluorescence radiation) are detected and counted in an integral way.One of the main differences between the SEICXRF 1 -3 method and the conventional 4,5 methods lies in the determination of the fluorescent radiation intensity emitted from a definite element; it is measured directly through the jump magnitude that occurs when the energy of the incident radiation is equal to the energy associated with one of the element absorption edges present in the sample. The main mechanisms that generate the characteristic photons as a function of fundamental parameters have great importance and are discussed in this paper. In addition, a specific algorithm is needed, which allows quantification of the fluorescent radiation emitted by the sample for each wavelength of the incident radiation.The effects and the criteria that have been taken into account to determine the jump magnitude corresponding to an element of interest are determined. The oscillating effect of the intensity at the absorption edge could be compensated for in most cases, and therefore it is not considered in the algorithms of the jump quantification. The spectrum is sequentially built up and its shape differs from the form of conventional XRF spectra. The proposed procedure for spectrum acquisition and elaboration brings together several advantages and inconveniences, which are discussed below. METHOD Excitation (selective excitation)The sample is excited with a monochromatic beam which is obtained by the Bragg diffraction of radiation from a primary x-ray source in a double-crystal arrangement device placed between the radiation source and the sample (see upperleft corner in Fig. 1). An x-ray tube or synchrotron 'white' radiation may be used as primary radiation source. The tilt angle of the crystal (Â) is changed in appropriate steps in order to scan the energy of the resulting monochromatic radiation in a range from 0.5 to several keV, depending on the analytical requirements, the sample nature and the crystal or multilayer structure. Detection (integral count)The detection is integral, so that all radiation emitted by the sample, no matter what its energy value, is counted. This may have some variants, for example the counting of the emitted radiation in the effective detection cone (Fig. 2) or the counting of the emitted radiation in all the emission solid angle (2 ) (Fig. 3). The latter alternat...

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“…Although the first discovery of E M S was in the early 1930s (Komig, 1931), the theoretical derivations of EXAFS were not reported until the early 1970s, using an expression based on singlescattering theory (Sayers, 1971;Sayers et al, 1974;Stem et al, 1975). Since then many good discussions on EXAFS theory have appeared (Eisenberger & Kincaid, 1978;Lee et al, 1981;Scott, 1984;Teo, 1986).…”

Section: Iif2 General Introduction To Exafsmentioning

confidence: 99%

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

Liang¹

1994

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EXAFS: New Horizons in Structure Determinations

Cited by 165 publications

References 45 publications

Stability of bulk metallic glass structure

Stability of bulk metallic glass structure

Selective excitation and integral counting of x‐ray fluorescence (SEICXRF)

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

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