Instruments Mossbauer spectroscopy

Solid-state detectors based on silicon- or germanium-diodes possess better resolution than gas counters, particularly when cooled with liquid nitrogen, but they allow only very low count rates. PIN diodes have also recently become available and have been developed for the instruments used in the examination of Martian soils (Sects. 3.3 and 8.3). A very recent development is the so-called silicon-drift detector (SDD), which has very high energy resolution (up to ca. 130 eV) and large sensitive detection area (up to ca. 1 cm ). The SNR is improved by an order of magnitude compared to Si-PIN detectors. Silicon drift detectors may also be used in X-ray florescence spectroscopy, even in direct combination with Mossbauer spectroscopy (see Sects. 3.3 and 8.3). 

The miniaturized Mossbauer instruments have proven as part of the NASA Mars Exploration Rover 2003 mission that Mossbauer spectroscopy is a powerful tool for planetary exploration, including our planet Earth. For the advanced model of MIMOS II, the new detector technologies and electronic components increase sensitivity and performance significantly. In combination with the high-energy resolution of the SDD, it will be possible to perform XRF analysis in parallel to Mossbauer spectroscopy. In addition to the Fe-mineralogy, information on the sample s elemental composition will be obtained. 

Introduce instrumental techniques used in analysis of the bioinorganic systems I will lecture on (Chapter 3 Instrumental and Computer-Based Methods). Typically, these would be electron paramagnetic resonance (EPR) and Mossbauer spectroscopies not often covered in undergraduate instrumental analysis courses plus X-ray diffraction and NMR techniques used for structural analyses of metalloproteins and their small molecule model compounds. 

The Mossbauer spectroscopy cell used in this investigation has been described in detail elsewhere (9). The Mossbauer spectroscopy instruments and the fitting routine used are also described elsewhere (9). All isomer shifts are reported relative to metallic iron at room temperature. 

It is the goal of this book to present in one place the key features, methods, tools, and techniques of physical inorganic chemistry, to provide examples where this chemistry has produced a major contribution to multidisciplinary efforts, and to point out the possibilities and opportunities for the future. Despite the enormous importance and use of the more standard methods and techniques, those are not included here because books and monographs have already been dedicated specifically to instrumental analysis and laboratory techniques. The 10 chapters in this book cover inorganic and bioinorganic spectroscopy (Solomon and Bell), Mossbauer spectroscopy (Miinck and Martinho), magnetochemical methods (Kogerler), cryoradiolysis (Denisov), absolute chiral structures (Riehl and Kaizaki), flash photolysis and studies of transients (Ferraudi), activation volumes (van Eldik and Hubbard), chemical kinetics (Bakac), heavy atom isotope effects (Roth), and computational studies in mechanistic transition metal chemistry (Harvey). 

Rancourt DG, Meschi C, Flandrois S (1986) S = 1/2 antiferromagnetic finite chains effectively isolated by frustration CuCl2 graphite intercalation compounds. Phys Rev B 33 347-255 Rancourt DG, Ping JY (1991) Voigt-based methods for arbitrary-shape static hyperfine parameter distributions in Mossbauer spectroscopy. Nuclear Instruments and Methods in Physics Research B (NIMB) 58 85-97... 

The aim of this chapter is to provide a brief background to Mossbauer spectroscopy within the context of phase transformations. The relevant parameters are summarised and the effect of temperature and pressure are discussed, particularly with reference to identifying phase transformations and characterising the electronic and structural environment of the Mossbauer nuclei. Instrumentation is summarised, particularly as it relates to in situ measurements of phase transformations, and a brief survey of applications is given. The appendix includes a worked example that illustrates the methodology of investigating a phase transformation using in situ Mossbauer spectroscopy. Numerous textbooks and review chapters have been written on Mossbauer spectroscopy, and a selection of the most relevant ones as well as some useful resources are listed in Table 1. 

Phase Transformations from Mossbauer Spectroscopi/ INSTRUMENTATION... 

E26.5 Since iron(V) would have the electron configuration of [Ar]3d, the ion would have three unpaired electrons. The logical choice would be either EPR (electron paramagnetic resonance) or Mossbauer spectroscopy. See Chapter 8, Physical Techniques in Inorganic Chemistry, for more discussion on both of these instruments. 

In recent years there have appeared several reviews in which Mossbauer spectroscopy of various biological iron compounds are discussed. For most of the experimental details, the reader is referred to the papers by DeBrunner (3), Weissbluth (4), Bearden and Dunham (5) and Lang (6). The review by Lang 6) is especially recommended since it deals with the paramagnetic hyperfine structure (PHS) observed in so many of these complexes and treats several different spin configurations. There are several excellent references concerning instrumentation one of the most recent is by Kalvius and Kankeleit (7). 

Other modem instrumental techniques, specifically, Mossbauer spectroscopy (20) and ion-scattering spectroscopy (ISS) (43, 67), as well as temperature-programmed reduction (TPR) (57) and temperature-programmed desorption (TPD) (24,25), have been used for characterization. Simple measurements of electrical resistivity can give useful information as well (23). 

One of the more difficult experimental aspects of Mossbauer spectroscopy is the accurate determination of the absolute velocity of the drive. The calibration is comparatively easy for constant-velocity instruments, but most spectrometers now use constant-acceleration drives. The least expensive method, and therefore that commonly used, is to utilise the spectrum of a compound which has been calibrated as a reference. Unfortunately, suitable international standards and criteria for calibration have yet to be decided. As a result, major discrepancies sometimes appear in the results from different laboratories. The problem is accentuated by having figures quoted with respect to several different standards, necessitating conversion of data before comparison can be made. However, calibration of data from an arbitrary standard spectrum will at least give self-consistency within each laboratory. 

On-line Instrumentation Applicable to the Coal Preparation Industry. Although numerous measurement concepts have been considered for on-line analysis in the coal preparation industry and several of these are being evaluated in the laboratory, e.g. Mossbauer spectroscopy ( ), x-ray diffraction, and x-ray fluorescence, this section will discuss only those systems that have undergone or are scheduled for field testing and are advertised as available. These include elemental analyzer systems, a moisture monitor, and a coal-rock-water slurry meter. 

The aim of this chapter is to report on recent advances in the in situ Mossbauer spectroscopy with synchrotron radiation on thin films that became possible due to the instrumentation developments at the nuclear resonance beamline ID 18 of the ESRF. After a detailed description of the beamline and of the UHV system for in situ experiments, a brief introduction into the basic NRS techniques is given. Finally, the application of these techniques to investigate magnetic, diffusion, and lattice dynamics phenomena in ultrathin epitaxial Fe films deposited on a W(l 10) substrate is presented and discussed. 

The spin and valence states of iron in the lower-mantle minerals have been investigated bya number of synchrotron X-ray and optical laser spectroscopic techniques in a high-pressure diamond anvil cell (DAC). Mossbauer spectroscopy has been instrumental in our understanding of this topic because this method is specific to Fe-containing minerals and provides hyperfine QS and CS parameters [5,19-22]. Specifically, synchrotron Mossbauer spectroscopy (SMS) with a highly intense and focused beam coupled with the X-ray transparent DAC permits in situ observations of the Mossbauer spectra with reasonable data collection times at extreme P-T conditions [20-22]. 

A further development in the field of Mossbauer spectra fitting and analysis is expected regarding the explanation of applicability of either continuous distributions of quadrupole splitting and hyperfine field or a superposition of discrete quadrupole doublets and magnetic sextets with models of multidomain and multilayer structures of the ferritin iron core. In this case, application of Mossbauer spectroscopy with a high velocity resolution may be used because it leads to a lower instrumental error in the determination of hyperfine parameters (this allows small variations of hyperfine parameters to be distinguished) as well as to a more reliable fitting of complicated Mossbauer spectra (see reviews [32,34-39, 128]). 

There have been a number of regional and international conferences devoted to industrial applications of Mossbauer spectroscopy or specific problems of materials science. The scope of problems addressed is extremely wide and ranges over all the above-mentioned problems. One can expect the contributions of Mossbauer spectroscopy in industry to divide into three areas (1) as a research tool, (2) in quality control, and (3) for in-service evaluation. Unfortunately, there are still very few Mossbauer instruments in use for quality control, or for in-service evaluation of materials or surface. More than 99% of Mossbauer publications cover use of the technique as a research tool. 

See also Mossbauer Spectrometers Mossbauer Spectroscopy, Applications Mossbauer Spectroscopy, Theory NQR, Theory Nuclear Quadrupole Resonance, Instrumentation. 

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