Quantum Chemistry and Mossbauer Spectroscopy

The underlying physics and analysis of Mossbauer spectra have been explained in detail in Chap. 4. In that chapter, the principles of how a spectrum is parameterized in terms of spin-Hamiltonian (SH) parameters and the physical origin of these SH parameters have been clarified. Many Mossbauer studies, mainly for Fe, have been performed and there is a large body of experimental data concerning electric-and magnetic-hyperfine interactions that is accessible through the Mossbauer Effect Database. 

However, useful as it is, ligand field theory is not a predictive first principles theory. Thus, it cannot be used to predict a priori the Mossbauer parameters of a given compound. Yet, the need to do so arises fi equently in Mossbauer spectroscopy. For example, if a reaction intermediate or some other unstable chemical species has been characterized by freeze quench Mossbauer spectroscopy and its SH parameters become available, then the question arises as to the structure of the unstable species. Mossbauer spectroscopy in itself does not provide enough information to answer this question in a deductive way. However, the more modest question which structures are compatible with the observed Mossbauer parameters can be answered if one is able to reliably predict Mossbauer parameters 

Giitlich et al., Mossbauer Spectroscopy and Transition Metal Chemistry, 

There may, however, be a number of other reasons to pursue a predictive first principles theory of Mossbauer spectroscopy. For example, one may want to elucidate structure/spectroscopy correlations in the cleanest way. To this end one may construct in the computer a number of models with systematic variations in oxidation states, spin states, coordination numbers, and identity of hgands to name only a few chemical degrees of freedom. In such studies it is immaterial whether these molecules have been made or could be made what matters is that one can find out which structural details the Mossbauer parameters are most sensitive to. This can provide insight into the effects of geometry or covalency that are very difficult to obtain by any other means. 

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During the many years of my teaching spectroscopy in chemistry and physics, Mossbauer spectroscopy has always been my favourite for several reasons The students become familiar with fundamental aspects on solid state and experimental physics, cry physics, quantum mechanics and theoretical chemistry to name a few. I consider it therefore highly recommendable, even necessary, that Mossbauer spectroscopy and relevant neighbouring fields are always part of the education in physics and chemistry. 

Since the discovery of the Mossbauer Effect many excellent books have been published for researchers and for doctoral and master level students. However, there appears to be no textbook available for final year bachelor students, nor for people working in industry who have received only basic courses in classical mechanics, electromagnetism, quantum mechanics, chemistry and materials science. The challenge of this book is to give an introduction to Mossbauer Spectroscopy for this level. 

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