Experiments and possibilities with super-intense Mössbauer sources

Mullen, J. G.; Wagoner, R. A.; Schupp, G.

doi:10.1007/bf02074266

Cited by 5 publications

(2 citation statements)

References 29 publications

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“…At room temperature, the ͑200͒ Bragg plane of LiF is a nearly 100% elastic scatterer of 46.5-keV ␥ rays 16,17 and so we can determine the recoilless fraction of the incident beam by scattering from LiF. The ratio of the recoilless fraction after scattering to the recoilless fraction before scattering is the elastic scattering fraction, and this, when multiplied by the total scattered intensity, determines the elastic intensity, and thus the DWF.…”

Section: Experimental Methods and Apparatusmentioning

confidence: 99%

Debye-Waller factors of alkali halides

1998

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Using very-high-intensity (ϳ70 Ci͒ 183 Ta Mössbauer sources, we have measured the Debye-Waller factors ͑DWF's͒ of sodium chloride, potassium chloride, and potassium bromide single crystals for several of the (h00) and (nnn) Bragg reflections. We have used an approach which properly accounts for thermal expansion over the temperature range of our experiment, from 90 K to 900 K, about 100 K below the melting point of our crystals. We have found that a procedure used to analyze data by earlier workers leads to incorrect parameters in the Debye-Waller factor exponent, and our procedure does not require empirical parameters to account for the effects of thermal expansion. Additionally, we find three items of significance. Contrary to earlier results, we observe that the cations and the anions have identical DWF's in NaCl and also in KBr. We observe terms in the expansion of the DWF exponential which are quartic in the scattering wave vector Q ជ in NaCl and KCl, with some evidence for a Q 4 term in KBr. The size of the Q 4 contribution is reported and varies with the direction of momentum transfer. We also observe that the Debye temperature and the coefficient of the anharmonic Q 2 term also vary with the direction of momentum transfer. We believe our data are the definitive evidence for a nonspherical thermal cloud in a cubic crystal; the ions have a larger amplitude of oscillation in the ͓h00͔ direction than in the ͓nnn͔ direction, contrary to the commonly held view of crystallographers that the most general form of the mean-square thermal motion is of an ellipsoid shape.

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Section: Experimental Methods and Apparatusmentioning

confidence: 99%

Debye-Waller factors of alkali halides

1998

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“…There have been many other studies of coherent interference in Mössbauer scattering. [2][3][4][5][6][7][8][9] In almost all of these studies, a detector was placed at a few angles near a Bragg peak, and an energy spectrum was measured. This was the method used in experiments by Kovalenko et al 10 and Nakai et al 11,12 who measured interference effects between Mössbauer nuclei having different hyperfine fields.…”

Section: Introductionmentioning

confidence: 99%

Mössbauer diffractometry on polycrystalline57Fe3Al

et al. 2002

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A Mössbauer powder diffractometer was used to measure diffraction patterns from polycrystalline foils of 57 Fe 3 Al. The intensities of Bragg diffractions were measured as a function of the energy of the incident photon. The bcc fundamental diffractions showed large changes in intensity as the incident energy was tuned through the nuclear resonances. These variations of diffraction intensity with incident energy were calculated with reasonable success using a kinematical theory of diffraction that included effects of coherent interference between x-ray Rayleigh scattering and, more importantly for these samples, Mössbauer scattering from nuclei having different hyperfine magnetic fields.

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Fultz

Stephens

1998

Hyperfine Interactions

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Experiments and possibilities with super-intense Mössbauer sources

Cited by 5 publications

References 29 publications

Debye-Waller factors of alkali halides

Debye-Waller factors of alkali halides

Mössbauer diffractometry on polycrystalline57Fe3Al

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