空气、N2和O2气体中瑞利-布里渊散射的系统研究
A systematic study of Rayleigh-Brillouin scattering in air, N2 and O2 gases
摘要：
自发瑞利-布里渊散射实验在空气中，N2和O2已经进行了广泛的温度和压力范围内的波长为403 nm，在90度的散射角。在高信噪比下对所有三种物质进行了瑞利-布里渊散射光谱分布的测量，产生了高质量的光谱，明确地显示了空气中散射与其成分N2和O2之间的微小差异。实验光谱与Tenti S6模型计算结果的比较表明，该模型具有较高的计算精度。在366 nm处进行先前测量之后，Tenti S6模型在此针对403 nm的第二波长进行验证。气体的体积粘度的值是通过优化模型的测量。它被验证，从先前的实验中获得的体积粘度参数在366 nm，是有效的波长为403 nm。此外，对于空气，这是作为一种单组分气体与有效的气体传输系数，Tenti S6处理验证为403 nm，如以前使用的波长366 nm，产生一个精确的模型描述的散射分布的温度和压力范围内，包括那些相关的大气研究。结果表明，Tenti S6模式可以应用于激光雷达探测大气风速和温度廓线分布。根据目前的研究结果，可以预测的光谱轮廓的一个典型的激光雷达后向散射几何形状，偏离约7%的纯高斯分布在现实的亚大气压发生在3-5公里的高度在地球的大气层。
英文摘要：
Spontaneous Rayleigh-Brillouin scattering experiments in air, N2 and O2 have been performed for a wide range of temperatures and pressures at a wavelength of 403 nm and at a 90 degrees scattering angle. Measurements of the Rayleigh-Brillouin spectral scattering profile were conducted at high signal-to-noise ratio for all three species, yielding high-quality spectra unambiguously showing the small differences between scattering in air, and its constituents N2 and O2. Comparison of the experimental spectra with calculations using the Tenti S6 model, developed in 1970s based on linearized kinetic equations for molecular gases, demonstrates that this model is valid to high accuracy. After previous measurements performed at 366 nm, the Tenti S6 model is here verified for a second wavelength of 403 nm. Values for the bulk viscosity for the gases are derived by optimizing the model to the measurements. It is verified that the bulk viscosity parameters obtained from previous experiments at 366 nm, are valid for wavelengths of 403 nm. Also for air, which is treated as a single-component gas with effective gas transport coefficients, the Tenti S6 treatment is validated for 403 nm as for the previously used wavelength of 366 nm, yielding an accurate model description of the scattering profiles for a range of temperatures and pressures, including those of relevance for atmospheric studies. It is concluded that the Tenti S6 model, further verified in the present study, is applicable to LIDAR applications for exploring the wind velocity and the temperature profile distributions of the Earth's atmosphere. Based on the present findings, predictions can be made on the spectral profiles for a typical LIDAR backscatter geometry, which deviate by some 7 percent from purely Gaussian profiles at realistic sub-atmospheric pressures occurring at 3-5 km altitude in the Earth's atmosphere.
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