Techniques

Diffusion Rayleigh

Rayleigh Scattering (RS) is an elastic scattering process. When the scattering particles are small compared to the wavelength of the incident light, the elastic scattering process is called Rayleigh Scattering (RS). That is the case for gas phase molecules and, therefore, this method is suited for laser imaging in gases. RS leads to images containing weighted information about the total gas density. It occurs from all constituent molecules. The scattered light is almost at the same wavelength as the incident light. Its use requires either constant gas composition or known mole fractions of all major species.   

Lorsque la composition et la pression du gaz sont connues, l’imagerie Rayleigh permet la mesure des champs de température planaires (Thermométrie Rayleigh). La diffusion Rayleigh est beaucoup plus faible que la diffusion de Mie mais plus de deux ordres de grandeur supérieure à la Diffusion Raman Spontanée (SRS). L’Incandescence des suies et la diffusion de Mie sont des processus qui peuvent complètement masquer le signal Rayleigh.