12. Laser Spectroscopy and Electron Beam Excitation

The advent of laser sources in the 1960s gave considerable impetus to the development of non-intrusive methods for the in situ determination of gas properties, including the velocity. These methods are based on physical processes related to the interaction between light and matter. The analysis of the resulting phenomena makes it possible to deduce the characteristics of the atoms and/or molecules composing the gas being tested and to measure properties such as its nature, concentration, energy levels, etc. Although these methods are not commonly used in aerodynamic applications because of their sophistication and limitations, they are powerful tools for studying complex flows. In particular, they give access to species concentration, local pressure, temperature and are of great interest for the study of very high temperature flows or flows containing chemically active combustion products.