727,258 research outputs found
Mössbauer Spectrometry
Mössbauer spectrometry gives electronic, magnetic, and structural information from within
materials. A Mössbauer spectrum is an intensity of γ-ray absorption versus energy for a
specific resonant nucleus such as ^(57)Fe or ^(119)Sn. For one nucleus to emit a Îł-ray and a second
nucleus to absorb it with efficiency, both nuclei must be embedded in solids, a phenomenon
known as the âMössbauer effect.â Mössbauer spectrometry looks at materials from the
âinside out,â where âinsideâ refers to the resonant nucleus.
Mössbauer spectra give quantitative information on âhyperfine interactions,â which are small
energies from the interaction between the nucleus and its neighboring electrons. The three
hyperfine interactions originate from the electron density at the nucleus (the isomer shift),
the gradient of the electric field (the nuclear quadrupole splitting), and the unpaired electron
density at the nucleus (the hyperfine magnetic field). Over the years, methods have been
refined for using these three hyperfine interactions to determine valence and spin at the
resonant atom. Even when the hyperfine interactions are not easily interpreted, they can
often be used reliably as âfingerprintsâ to identify the different local chemical environments
of the resonant atom, usually with a good estimate of their fractional abundances. Mössbauer
spectrometry is useful for quantitative phase analyses or determinations of the concentrations
of resonant element in different phases, even when the phases are nanostructured or
amorphous.
Most Mössbauer spectra are acquired with simple laboratory equipment and a radioisotope
source, but the recent development of synchrotron instrumentation now allow for measurements
on small 10 ”m samples, which may be exposed to extreme environments of pressure
and temperature. Other capabilities include measurements of the vibrational spectra of the
resonant atoms, and coherent scattering and diffraction of nuclear radiation.
This article is not a review of the field, but an instructional reference that explains principles
and practices, and gives the working materials scientist a basis for evaluating whether or not
Mössbauer spectrometry may be useful for a research problem. A few representative
materials studies are presented
Assessing depleted uranium (DU) contamination of soil, plants and earthworms at UK weapons testing sites
Depleted uranium (DU) weapons testing programmes have been conducted at two locations within the UK. An investigation was therefore carried out to assess the extent of any environmental contamination arising from these test programmes using both alpha spectrometry and mass spectrometry techniques. Uranium isotopic signatures indicative of DU contamination were observed in soil, plant and earthworm samples collected in the immediate vicinity of test firing points and targets, but contamination was found to be localised to these areas. The paper demonstrates the superiority of the 235U:238U ratio over the 234U:238U ratio for identifying and quantifying DU contamination in environmental samples and also describes the respective circumstances under which alpha spectrometry or mass spectrometry may be the more appropriate analytical tool
Recovery and reanalysis of archived airborne gamma spectrometry data from the 1991 Dounreay survey
Archived Airborne Gamma Spectrometry (AGS) data from the 1991 NIREX characterisations of Caithness have been recovered. The separate gamma spectrometry and positional data streams for approximately 120000 measurements have been combined into a single data stream using the European Radiometrics and Spectrometry (ERS) data format. An analysis using working calibration coefficients and spectral stripping procedure has verified that the original survey recorded high quality data. The converted data stream is in a format more accessible to future research use, including evaluation of environmental change in the Caithness region
Etalon Array Reconstructive Spectrometry.
Compact spectrometers are crucial in areas where size and weight may need to be minimized. These types of spectrometers often contain no moving parts, which makes for an instrument that can be highly durable. With the recent proliferation in low-cost and high-resolution cameras, camera-based spectrometry methods have the potential to make portable spectrometers small, ubiquitous, and cheap. Here, we demonstrate a novel method for compact spectrometry that uses an array of etalons to perform spectral encoding, and uses a reconstruction algorithm to recover the incident spectrum. This spectrometer has the unique capability for both high resolution and a large working bandwidth without sacrificing sensitivity, and we anticipate that its simplicity makes it an excellent candidate whenever a compact, robust, and flexible spectrometry solution is needed
Characterization of Polyphosphoesters by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
FT-ICR mass spectrometry, together with collision-induced dissociation and electron capture dissociation, has been used to characterize the polyphosphoester poly[1,4-bis(hydroxyethyl)terephthalate-alt-ethyloxyphosphate] and its degradation products. Three degradation pathways
were elucidated: hydrolysis of the phosphateâ[1,4-bis(hydroxyethyl)terephthalate]bonds; hydrolysis of the phosphateâethoxy bonds; and hydrolysis of the ethylâterephthalate bonds. The dominant degradation reactions were those that involved the phosphate groups. This work constitutes the first application of mass spectrometry to the characterization of polyphosphoesters and demonstrates the suitability of high mass accuracy FT-ICR mass spectrometry, with CID and ECD, for the structural analysis of polyphosphoesters and their degradation products
Utility of mass spectrometry for the diagnosis of the unstable coronary plaque.
Mass spectrometry is a powerful technique that is used to identify unknown compounds, to quantify known materials, and to elucidate the structure and chemical properties of molecules. Recent advances in the accuracy and speed of the technology have allowed data acquisition for the global analysis of lipids from complex samples such as blood plasma or serum. Here, mass spectrometry as a tool is described, its limitations explained and its application to biomarker discovery in coronary artery disease is considered. In particular an application of mass spectrometry for the discovery of lipid biomarkers that may indicate plaque morphology that could lead to myocardial infarction is elucidated
Detection of Trace Amounts of Toxic Metals in Environmental Samples by Laser-excited Atomic Fluorescence Spectrometry
Results for the direct determination of trace amounts of Pb and Cd in Antarctic and Greenland ancient ice and recent snow by laser-excited atomic fluorescence spectrometry (LEAFS) are presented. The whole procedure starting from field sampling, mechanical decontamination of the samples in an ultra-clean laboratory and final analysis of the decontaminated samples is described. The measured concentrations varied in the ranges 0.1â3 pg ml^(â1) for Cd and 0.3â30 pg ml^(â1) for Pb. The results for direct analysis by LEAFS agree favourable with those obtained by isotope dilution mass spectrometry and electrothermal atomic absorption spectrometry, which require time-consuming pre-treatment and pre-concentration stages
Isotope ratio - Mass spectrometry
Podeu consultar el llibre complet a: http://hdl.handle.net/2445/32166This article summarizes the configurations involving isotope ratio mass spectrometry (IRMS) technology available at the CCiTUB and the wide range of possible applications. Some examples of these applications are shown
- âŠ