Precision measurements of the Debye-Waller factor of Fe57 in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error arises from Au Ly x-rays which are unresolved by the radiation detection system from the 14.4 KeV gamma ray. The K absorption edge of Br has been used to correct for the presence of x-rays. These measurements have revealed the existence of two nonequivalent lattice sites which the Co57 impurity (parent of Fe57) may occupy. One of the sites has been populated by quenching the source from temperatures greater than 1150 K and has been identified as a substitutional lattice site. From an analysis of the Mössbauer spectrum it is concluded that some of the substitutional sites may be in the vicinity of dislocations. It has been determined that the impurity-host force constant for Fe57 atoms in the substitutional site is about the same as the host-host force constant; the experimental value of the anharmonicity parameter ɛ (-2) for Fe57 in the Au is nearly the same as calculated values of ɛ (-2) for pure Au. The second site forms very slowly upon annealing the source at intermediate temperatures and has been identified as being interstitial in character. The slow rate of formation of the interstitial site indicates that diffusion is a primary mechanism in its formation. The second site must therefore be more complicated than an ordinary interstitial. It is proposed that this site is a split, or dumbbell, interstitial formed by substituting two impurity atoms for one of the Au atoms.

Thèse de doctorat : Sciences : Paris 12 : 2003. / Titre provenant de l'écran-titre.

Thesis--University of California, Berkeley, 1963. / "UC-4 Chemistry" -t.p. "TID-4500 (18th Ed.)" -t.p. Includes bibliographical references (p. 66-68).

Undergraduate honors paper--Mount Holyoke College, 2006. Program in Geochemistry. / Includes bibliographical references (leaves 84-89).

Th.--Sci. phys.--Paris 11--Orsay, 1983. N°: 2698.

Two independent Fe³⁺ species have been simultaneously introduced into Linde L zeolite. One is an exchanged Fe³⁺ species while the other is the molecular species FeCI₃, By simpIe outgassing at 573°K, the exchanged Fe³⁺ is reduced to Fe²⁺. By sweeping the system at 523°K with H₂, both species are converted to ferrous and, at 573°K, the exchanged species is reduced to Feº and the FeCI₃ is reduced to FeCI₂. Outgassing the latter system at 573°K oxidizes the Feº to Fe₂O₃ while the FeCI₂ remains intact. These valency changes were examined using Mössbauer Spectroscopy and, using this technique, a Morin transition appears to have been detected in the Feº species. / Science, Faculty of / Chemistry, Department of / Graduate

A study was undertaken to investigate the solid-state structure of about 25 triphenyltin carboxylates, Ø₃SnOCOR. The compounds were synthesized and then analyzed by Mössbauer and infrared spectroscopy. The compounds were divided into three series on the basis of the nature of the R group. The first series of compounds had R groups which were "linear" chain hydrocarbons ranging in length from one carbon atom (triphenyltin formate) to eighteen carbon atoms (triphenyltin stearate). In the second series several compounds had methyl branches at various positions along the hydrocarbon chain, some had longer alkyl groups and a few had a methylene group bonded to the a-carbon atom. The third series contained mono-, di-, and tri- substituted haloacetates. These compounds were prepared in order to test the assumption that bulky R groups would prevent (by steric interaction) polymer formation in the solid. The polymeric structure which is commonly found for triorganotin carboxylates consists of pentacoordinate Sn atoms. Each carboxylate group bridges between two different Sn atoms and this occurs indefinitely to form a polymer. Steric interaction of the R group with neighbouring phenyl groups (bonding to Sn) could prevent polymer formation. The resulting structure would be monomeric and have a tetracoordinate Sn atom and a terminal carboxylate group like that for an organic ester. The majority of compounds were found to be polymeric solids. Structural changes (polymeric to monomeric) were observed for a few compounds and this could be attributed to steric interaction. The Mössbauer and infrared data were complimentary and conclusive when used to differentiate between the two possible structural types. In a polymeric structure the Sn atom can be visualized as being in a trigonal bipyramidal environment in which the oxygen atoms are axial and the phenyl groups equatorial. Using the above idealized structural type it was possible to test a point-charge model which had been used to predict quadrupole splitting values, Δ. The model was tested for the triphenyltin haloacetates and found to give fairly good agreement with the observed quadrupole splitting values. / Science, Faculty of / Chemistry, Department of / Graduate

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Thèse de doctorat : Physique : Paris 12 : 2003. Thèse de doctorat : Physique : Université Babes-Bolyai Cluj-Napoca : 2003. / Version électronique uniquement consultable au sein de l'Université Paris 12 (Intranet). Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. en fin de chapitre.

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