Introduction to Analytical Methods in Organic Geochemistry by Jan Schwarzbauer & Branimir Jovančićević

Author:Jan Schwarzbauer & Branimir Jovančićević
Language: eng
Format: epub
ISBN: 9783030385927
Publisher: Springer International Publishing

4.3 Spectroscopy

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Information about molecular properties and structural moieties can be obtained by spectroscopic analyses. Based on the interaction of electromagnetic radiation with molecules various energies become excited and the corresponding absorption is measured. The physical basics, the technical realization but especially the interpretation of spectra are described in this chapter.

4.3.1 Principles of Spectroscopy

Spectroscopy is used as very valuable tool to gain insights into the structural properties of organic molecules. The method is based on a very simple physical phenomenon, the interaction of electromagnetic radiation and matter, also known as ‘absorption’ and its counterpart ‘emission’. Since this interaction occur on molecular or atomic dimensions, it can be explained only by quantum mechanics. For this purpose, electromagnetic radiation can be described either as particle beam or as a wave, the so-called wave-particle dualism. For describing the spectroscopic processes, the most important aspect is the quantization implying only discrete energy states in molecular systems. Hence, changing any energy state in molecules is only possible by adding a corresponding energy package. With respect to absorption processes and describing electromagnetic radiation as particles, the absorption is only possible if the energy of the absorbed photon fits exactly the energy difference between initial or ground state and excited state (as exemplified in Fig. 4.33). Since many energy states and their distances depend on the molecular structures and atomic properties, the absorption energy can provide information on molecule and atom characteristics. This is the basic approach of analytical spectroscopy.

Fig. 4.33Basic principles of photon absorption and excited energy states in molecules

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