Spontaneous Rayleigh–Brillouin scattering of ultraviolet light in nitrogen, dry air, and moist air

Abstract

Atmospheric lidar techniques for the measurement of wind, temperature, and optical properties of aerosols rely on the exact knowledge of the spectral line shape of the scattered laser light on molecules. We report on spontaneous Rayleigh-Brillouin scattering measurements in the ultraviolet at a scattering angle of 90 degrees on N(2) and on dry and moist air. The measured line shapes are compared to the Tenti S6 model, which is shown to describe the scattering line shapes in air at atmospheric pressures with small but significant deviations. We demonstrate that the line profiles of N(2) and air under equal pressure and temperature conditions differ significantly, and that this difference can be described by the S6 model. Moreover, we show that even a high water vapor content in air up to a volume fraction of 3.6vol.% has no influence on the line shape of the scattered light. The results are of relevance for the future spaceborne lidars on ADM-Aeolus (Atmospheric Dynamics Mission) and EarthCARE (Earth Clouds, Aerosols, and Radiation Explorer).

Coherent and spontaneous Rayleigh-Brillouin scattering in atomic and molecular gases and gas mixtures

“…W hile such an approach may work, it is not internally consistent because the effective kinetic param eters are not w ell defined, and an agreem ent betw een m odel and experim ent m ust b e deem ed fortuitous. Still, in a separate study on spontaneous Rayleigh-B rillouin scattering on dry and m oist air, m easured spectra could be w ell-represented by the Tenti S6 model, taking the effective transport coefficients of air as param eters [32] .…”

A Rayleigh-Brillouin scattering spectrometer for ultraviolet wavelengths

“…11,12 The calculated S6 curves are convolved with the measured instrument function of width 232 MHz; the fact that the series of overlapping RB-profiles measured by the FPI never reaches the zero level is accounted for (see also Ref. 11).…”

“…In particular, in recent studies, the 6-component version of the Tenti-model 10 (Tenti S6) was found to accurately describe the RB-scattering profile in various atomic and molecular gases 11 and in air. 12 The RB-scattering profile can be measured by different means. The direct method analyzes the scattered light via a Fabry-Perot interferometer, as was pursued in the early studies.…”

The Measurement of Tropospheric Temperature Profiles using Rayleigh-Brillouin Scattering: Results from Laboratory and Atmospheric Studies

“…In 1974, Tenti et al [6] developed a modelthe so-called Tenti S6 model -for describing RB spectra of light scattered in molecular gases of single species, which is since then considered as the best model available. Recently performed laboratory studies [7][8] into account the mixed nature of air as scattering medium. In order to retrieve temperature from measured RB profiles, they have to be analyzed with the Tenti S6 model in a certain optimization procedure as for instance a least-squares fit with temperature as free fitting parameter.…”