Experiments on spontaneous Rayleigh-Brillouin scattering in air

Abstract

Atmospheric lidar techniques for the measurement of wind, temperature, and optical properties of aerosols as well as non-intrusive measurement techniques for temperature, density and bulk velocity in gas flow rely on the exact knowledge of the spectral line shape of the scattered laser light on molecules. The best model currently available to describe these line shapes is the Tenti S6 model which, however, has not yet been validated in air. In this thesis, high-precision spontaneous Rayleigh-Brillouin (SRB) scattering experiments on N2 as well as on dry and humid air are presented and used to prove the accuracy of the Tenti S6 line shape model and to investigate the influence of water vapour on the SRB line shape. The measurements were performed in controlled laboratory experiments as well as in the atmosphere. In contrast to earlier SRB scattering experiments in the visible spectral region, the measurements were carried out with ultraviolet light, which is used by the lidars on the satellite missions ADM-Aeolus and EarthCARE.