Mossbauer spectroscopy background

Atoms are not rigidly bound to the lattice, but vibrate around their equilibrium positions. If we were able to look at the crystal with a very short observation time, we would see a slightly disordered lattice. Incident electrons see these deviations, and this, for example, is the reason that in LEED the spot intensities of diffracted beams depend on temperature at high temperatures the atoms deviate more from their equilibrium position than at low temperatures, and a considerable number of atoms are not at the equilibrium position necessary for diffraction. Thus, spot intensities are low and the diffuse background high. Similar considerations apply in other scattering techniques, as well as in EXAFS and in Mossbauer spectroscopy. 

The presence of hydrous ferric oxide (FeOOH) has been confirmed by X-ray diffraction, Mossbauer spectroscopy, and magnetization measurements (7). Figure 11 shows the X-ray diffraction patterns for the region of 20 between 14 and 18°. The two peaks at 15.2 and 16.3° are diffractions from a-Fe203, but the large background is from the various forms of hydrous ferric oxide. The lack of fine structure excludes the possibility of identifying... 

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. 

Weyer [50] developed a conversion electron detector based on a PPAC for Mossbauer spectroscopy. Conversion electrons are emitted from the surbce of a Mossbauer absorber after resonance absorption with a conversion coefficient a (a = 8.2 for 14.4 keV Fe). In principle, a conversion electron detector is very sensitive only for resonant Mossbauer 7-rays without interference of nonresonant 7-radiations. The PPAC is importantfor in-beam Mossbauer spectroscopy of implanted excited atoms and Rl nuclei in environments with high backgrounds. 

Background of Mossbauer Spectroscopy and Its Application to Magnetism in Uranium Compounds... 

This first chapter provides an introduction to Mossbauer spectroscopy and a background for the subsequent chapters. Hence the next few pages contain a general discussion of the Mossbauer effect, the conditions necessary for its observation, and the way in which Mossbauer... 

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