2,695 research outputs found
Comparison of conventional and total reflection excitation geometry for fluorescence -ray absorption spectroscopy on droplet samples
No full textX-ray absorption fine structure (XAFS) experiments in fluorescence mode have been performed in total reflection excitation geometry and conventional 45°/45° excitation/detection geometry for comparison. The experimental results have shown that XAFS measurements are feasible under normal total reflection X-ray fluorescence (TXRF) conditions, i.e. on droplet samples, with excitation in grazing incidence and using a TXRF experimental chamber. The application of the total reflection excitation geometry for XAFS measurements increases the sensitivity compared to the conventional geometry leading to lower accessible concentration ranges. However, XAFS under total reflection excitation condition fails for highly concentrated samples because of the self-absorption effect
Gerald Gorman
No full textPhorograph - Gerald Gorman in traditional Scottish clothing, (Edinburgh, Scotland). A note with the picture reads: "Hoot Mon", The Canadian Kid. Sincerely Yours, Gerald Gorma
Gerald Nelson discusses article "Do roads cause deforestation?"
No full textIFPRI Senior Researcher, Gerald Nelson, discusses the article, "Do roads cause deforestation." On July 25, 2011, Nelson and co-author, Daniel Hellerstein, were honored by the AAEA with the Publication of Enduring Quality Award for this innovative 1997 publication on techniques for turning satellite imagery into economic data
Portrait of President Gerald Ford.
No full textHandwritten Inscription: \u27To Felton M. Johnston - best always, Gerald Ford\u27https://egrove.olemiss.edu/fmjohnston/1097/thumbnail.jp
Comparison of synchrotron radiation total reflection X-ray fluorescence excitation–detection geometries for samples with differing matrices
No full text
Gerald Costanzo
No full textGerald Costanzo visited The College at Brockport in June 1984. He is a poet and publisher, and has been a faculty member at Carnegie Mellon University since 1970.Archived web contentSUNY BrockportWriters Forum Author Photo
Parameter study of self-absorption effects in Total Reflection X-ray Fluorescence–X-ray Absorption Near Edge Structure analysis of arsenic
No full textTotal reflection X-ray Fluorescence (TXRF) analysis in combination with X-ray Absorption Near Edge
Structure (XANES) analysis is a powerful method to perform chemical speciation studies at trace element
levels. However, when measuring samples with higher concentrations and in particular standards, damping
of the oscillations is observed. In this study the influence of self-absorption effects on TXRF–XANES
measurements was investigated by comparing measurements with theoretical calculations. As(V) standard
solutions were prepared at various concentrations and dried on flat substrates. The measurements showed a
correlation between the damping of the oscillations and the As mass deposited. A Monte-Carlo simulation
was developed using data of the samples shapes obtained from confocal white light microscopy. The results
showed good agreement with the measurements; they confirmed that the key parameters are the density of
the investigated atom in the dried residues and the shape of the residue, parameters that combined define
the total mass crossed by a certain portion of the incident beam. The study presents a simple approach for
an a priori evaluation of the self-absorption in TXRF X-ray absorption studies. The consequences for Extended
X-ray Absorption Fine Structure (EXAFS) and XANES measurements under grazing incidence conditions are
discussed, leading to the conclusion that the damping of the oscillations seems to make EXAFS of
concentrated samples non feasible. For XANES “fingerprint” analysis samples should be prepared with a
deposited mass and sample shape leading to an acceptable absorption for the actual investigation
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