Following the discovery almost half a century ago of the resonant emission and absorption of gamma rays in 191Ir by Rudolf Mössbauer (Mossbauer, ), the effect that takes his name has been utilized by many studies to explore a wide range of elements and minerals. Recently, a renewed interest in the application of Mössbauer spectroscopy in geosciences, particularly with regard to nanomaterials and Mars (Klingelhöfer et al., ), has led to the technique becoming an increasingly important tool. This is especially true for 57Fe mineralogy, where the technique is capable of selectively determining the oxidation state and mineralogy of Fe in samples of environmental soils and sediments, which might be dominated by a wide range of mineral phases that might not ordinarily be measurable with conventional techniques.
The purpose of this chapter is to give a general overview of Mössbauer spectroscopy to the non-specialist. While there are many elements that are able to undergo the Mössbauer effect, we focus on 57Fe in particular in order to help encourage its use in the field of geomicrobiology. As such, many important factors will not be covered here, and the reader is encouraged to look at additional material to obtain a more comprehensive understanding of the theory of Mössbauer spectroscopy. Some example reviews include references (Dyar et al., ; Greenwood and Gibb, ; Gütlich et al., , ; Murad and Cashion, ). Furthermore, when considering whether the technique is potentially useful in a study, it is always advisable to combine the results and observations obtained through Mössbauer spectroscopy with information obtained through diffraction, imaging, or synchrotron-based techniques to obtain a complete story of the nature of a sample. This chapter has been broken up into separate sections, including a brief introduction to the theory behind Mössbauer spectroscopy; the parameters that are obtained from each spectrum and provide the necessary information required for fitting; some experimental details about how measurements are carried out and should be prepared; and finally, the applications of the technique and how it can be used to determine the oxidation states and mineral identities of samples.
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