氮气CARS理论光谱简化计算及应用

Simplified calculation and application of nitrogen CARS theoretical spectrum

基于量子理论,对相干反斯托克斯喇曼散射(CARS)的机理进行了探讨,对氮气分子喇曼散射截面、不同能级分子布居数密度差、振转配分函数及三阶非线性极化率的计算进行了讨论。对氮气CARS理论光谱的计算进行了合理简化,并给出了计算模型。仿真结果表明,适当的简化能显著提高理论光谱计算速度。计算结果与其他文献中未简化的氮气CARS计算结果较接近,能用于CARS测量。设计了单脉冲CARS装置,并用简化模型进行了不同压力条件下实验研究。理论光谱分辨率0.1 cm-1,光谱采样频率10 Hz,单次测量时间10 ns,测量误差小于10%。

Based on quantum theory, Coherent anti-Stokes Raman spectroscopy （CARS） mechanics was discussed. The parameter calculation of nitrogen CARS spectrum such as Raman scattering section, molecule population density difference between lower and upper vibration level, rotational and vibrational fraction function and three-order nonlinear susceptibility was analyzed. Reasonable simplifications make the calculation process much quicker. The calculation model was given. The simulation results show that reasonable simplification method can improve calculation velocity of CARS spectroscopy. Nitrogen CARS spectrum calculation results are in agreement with those in other hteratures. Single-pulse CARS setup used for transient temperature distribution measurement was designed. Measurement results under different conditions show that theoretical spectral resolution can be up to 0. 1 cm^-1, the sample repetition rate is 10 Hz,single measurement time is about 10 ns and measurement error is less than 10%.