Abstract Raman spectroscopy has gone through several stages of development linked with improvements in technology, especially in electronics, lasers, filters and detectors. Many commercially available instruments are easy to use and have become plug-and-play instruments that are now widespread in many Earth science and Cultural Heritage laboratories, but the basic theory on which the instruments are based is often poorly known, which can result in poor use or poor choice of instrument. This chapter is intended to summarize the instrument specifications imposed by Raman spectroscopy and to summarize the basic knowledge and theory for the main components of a Raman spectrometer. The second section focuses on instrument calibration for correct use of the instrument. It contains both theoretical and experimental parts. Finally, different types of Raman spectrometers are described along with their coupling to other techniques such as LIBS and laser-induced fluorescence.

Abstract Geological fluids are the major agents of transport of matter and heat in Earth dynamics. Unlike minerals, fluid density may vary by an order of magnitude, resulting in drastic changes in the molecular interactions. Water is a major fluid component, so it is essential to understand the response of hydrogen bonding with respect to pressure and temperature. In addition, geological fluids can be classified as complex chemical systems by a mixture of molecular compounds and ions. Thus, the study of aqueous solutions plays a fundamental role in understanding the behaviour of geological fluids. In the present chapter, focus is first placed on the use of Raman spectroscopy in the study of gases and how their spectral response changes under different pressure/temperature conditions. The ability of Raman spectroscopy to detect structural changes occurring in hydrogen-bonded systems, under thermodynamic conditions ranging from ordinary to extreme pressures and/or temperature is then discussed. Raman spectroscopy will be shown to provide invaluable information for a better understanding of the role played by geological fluids in Earth and crustal processes.