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Spontaneous Rayleigh-Brillouin scattering experiments in air, N2 and O2 havebeen performed for a wide range of temperatures and pressures at a wavelengthof 403 nm and at a 90 degrees scattering angle. Measurements of theRayleigh-Brillouin spectral scattering profile were conducted at highsignal-to-noise ratio for all three species, yielding high-quality spectraunambiguously showing the small differences between scattering in air, and itsconstituents N2 and O2. Comparison of the experimental spectra withcalculations using the Tenti S6 model, developed in 1970s based on linearizedkinetic equations for molecular gases, demonstrates that this model is valid tohigh accuracy. After previous measurements performed at 366 nm, the Tenti S6model is here verified for a second wavelength of 403 nm. Values for the bulkviscosity for the gases are derived by optimizing the model to themeasurements. It is verified that the bulk viscosity parameters obtained fromprevious experiments at 366 nm, are valid for wavelengths of 403 nm. Also forair, which is treated as a single-component gas with effective gas transportcoefficients, the Tenti S6 treatment is validated for 403 nm as for thepreviously used wavelength of 366 nm, yielding an accurate model description ofthe scattering profiles for a range of temperatures and pressures, includingthose of relevance for atmospheric studies. It is concluded that the Tenti S6model, further verified in the present study, is applicable to LIDARapplications for exploring the wind velocity and the temperature profiledistributions of the Earth's atmosphere. Based on the present findings,predictions can be made on the spectral profiles for a typical LIDARbackscatter geometry, which deviate by some 7 percent from purely Gaussianprofiles at realistic sub-atmospheric pressures occurring at 3-5 km altitude inthe Earth's atmosphere.

A systematic study of Rayleigh-Brillouin scattering in air, N2 and O2 gases