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General introduction

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Raman spectroscopy belongs to the group of vibrational spectroscopic methods. Vibrational spectroscopy is sensitive to the vibrations (periodic oscillations) of chemically bound atomic pairs or groups in molecules or crystals. Thus, these methods are able to reveal both chemical and local structural information. Raman scattering is the inelastic scattering of light from certain vibrations of chemical bonds or atomic groups. In Raman spectroscopy, the feeble, low-intensity light is investigated that comes from such interactions. Differences in the compositon or the structure of matter show up in the intensity pattern of scattered light, therefore the Raman spectrum of each molecule or solid is unique. This property can be used for easy, quick phase identification ("fingerprint" method). The spectral parameters of certain spectral bands may be used to quantify physical and chemical properties (such as strain, defect density, chemical substitutions etc.). Raman analysis is non-destructive and non-invasive, in the simplest case no sample preparation is needed. Everything can be measured in a Raman microspectrometer of which the microscope is able to form an image. A motorised stage enables the instrument to map the distribution of phases or properties in space (xy, xz/yz or even xyz dimensions) with micrometer resolution. With special extensions the Raman microspectrometer can analyse large objects (e.g. archeological artefacts) or even liquids as well.