X-ray absorption studies

Tyliszczak T, Hitchcock A, Wu S, Chen A, Szymanski G and Lipkowski J 1998 X-ray absorption studies of mixed overlayers formed by copper adatom co-adsorbed with anions at the Au(111) electrode surface Synchrotron Radiat. News 11 31-8... 

Roentgen, definition of the, 248 Roentgen, W. C., discovery and investigation of x-rays by, 2, 9-12, 43 Nobel Prize awarded to, 2 production of secondary x-rays by, 12 x-ray absorption studies by, 11 x-ray papers of, 2... 

Sham, T.-K. X-Ray Absorption Studies of Liquids Structure and Reactivity of Metal Complexes in Solution and X-Ray Photoconductivity of Hydrocarbon Solutions of Organometallics, 145, 81-106(1987). 

We next discuss x-ray absorption studies. To put matters in context, it is useful to understand that conventional studies using Auger electron spectroscopy (AES) and x-ray photoemission spectroscopy (XPS) can be carried out only ex situ in high vacuum after electrochemical treatment since the techniques involve electron detection. X-ray absorption spectroscopy can, in contrast, be used for valence and structural environment studies. As x-rays only are involved, they can be carried out in situ in an electrochemical or similar cell. 

X-ray Absorption Study of Vanadium in Fluid Cracking Catalysts... 

Hayes, KF. Papelis, C. Leckie, J.O. (1988) Modeling ionic strength Effects on anion adsorption at hydrous oxide/solution interfaces. J. Colloid Interface Sd. 78 717—726 Hayes, KF. Roe, A.L. Brown, G.E. Hodgson, KO. Leckie, J.O. Parks, G.A. (1987) In-situ X-ray absorption study of surface complexes Selenium oxyanions on a-FeOOH. Sdence 238 783-786... 

While the stability of the monolayer Pt alloy catalyst concept was initially unclear and therefore threatened to make the monolayer catalyst concept a questionable longer term solution, a very recent discovery seems to lend support to the claim that Pt monolayer catalyst could be made into stable catalyst structures Zhang et al. [94] reported the stabilizing effect of Au clusters when deposited on top of Pt catalysts. The presence of Au clusters resulted in a stable ORR and surface area profile of the catalysts over the course of about 30,000 potential cycles. X-ray absorption studies provided evidence that the presence of the Au clusters modified the Pt oxidation potentials in such a way as to shift the Pt surface oxidation towards higher electrode potentials. 

X-ray absorption study of tribofilms generatedfrom a combination of ZDDP and borate-sulfonate RMs was used to determine the chemistry of tribochemical films at the surface and the bulk The calcium phosphate content in the tribofilm generated from either ZDDP + borate-sulfonate RMs or from ZDDP + calcium sulfonate soft-core RMs is similar (Varlot et al., 2001). Calcium sulfonate S(+5) undergoes disproportion reaction to form sulfate S(+6) and sulfite S(+4), and the presence of ZDDP affects the disproportion process. Close to the steel surface, the... 

Manceau, A. Calas, G. (1986) Nickel-bearing clay minerals 2. Intracrystalline distribution of nickel An X-ray absorption study. Clay Minerals, 21, 341-60. 

Another example is the adsorption of prochiral 1,2,4-benzene tricarboxylic acid on Cu(100). As determined via X-ray absorption studies, this molecule has a tilted local geometry on the surface. The adsorbate complex is therefore chiral [70]. The long range ordered adlattice, however, has p(3 x 3) periodicity i.e., the molecules are strictly aligned by the quadratic substrate mesh. 

Meinike, C., Sole, A., Pospisil, P., Dau, H. (2000) does the structure of the water-oxidizing Photosystem II-Manganese complex at room temperature differ from its low-temperature structure A comparative X-ray absorption study, Biochemistry 39, (24)... 

In cases where there is a low concentration of cation of interest, if the cations are highly disordered in the zeolite framework, or if good crystalline samples are unavailable, atom specific or environment-specific spectroscopic probes may be preferable to determine local structures about the cation in the zeolite. NMR (4), IR ( 5, 6) ESR (7-10), optical (9,10), MSssbauer effect (11-15), and x-ray absorption studies (2,16,17,18) have been used to determine cation microenvironments. In particular, it has been shown that EXAFS (Extended X-ray Absorption Fine Structure) of the cation can often be used to give direct structure information about cation environments in zeolites, but EXAFS techniques, while giving radial distances and relative coordination numbers, are insensitive to site symmetry and cannot, in general, give both coordination numbers and relative site populations. Clearly it is desirable to use complementary spectroscopic techniques to fully elucidate the microenvironments in dilute, polycrystalline zeolite systems. 

X-Ray Absorption Studies of Monometallic Supported Metal Catalysts... 

X-Ray absorption studies have also been applied to the determination of the electronic structure of Fe and Cu in spinels (113) and to clear up the relations in a dispersed manganese dioxide oxidation catalyst (cf. Section V,I) (51). 

The CoMo/A1203 catalyst system has been studied by a variety of techniques in attempts to relate structural features of the system to catalytic performance. It is a remarkable property of this catalyst that despite high metal loading (about 15-20 wt.% based on oxides), poor crystallinity is developed. Consequently, traditional methods provide little information about the local structure of Mo and Co in these industrial catalysts and about structural changes with the preparative method. It is obvious that X-ray absorption studies are appropriate means for their characterization. 

X-RAY ABSORPTION STUDY OF ELECTRONIC, SPATIAL STRUCTURE AND PROPERTIES OF BaLiiiMnjO, MANGANATES... 

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