基于LIBS的CN自由基B^2Σ^+～X^2Σ^+光谱及温度研究

Study on B^2Σ^+～X^2Σ^+ spectra and temperature of CN radicals based on LIBS

为了研究CN自由基B^2Σ^+~X^2Σ^+光谱及温度随着条件的变化规律,采用激光诱导击穿光谱的方法,击穿空气环境下的高纯石墨产生CN自由基,并用高分辨率光谱仪测量其B^2Σ^+~X^2Σ^+的发射光谱,改变激光能量和激光焦点位置研究不同条件下的CN自由基光谱。结果表明,激光能量从30mJ调谐到50mJ,增加步长为5mJ,光谱强度随着激光能量的增大变强;单脉冲能量为50mJ时光谱强度达到最大值;此外,测量光谱在样品上表面到焦点距离为8mm时,信噪比达到最大值;利用LIFBASE软件对光谱数据进行拟合,得出CN自由基的振动温度的量级约为10 4K,转动温度约为4000K;CN自由基的振动温度随着距离的增加整体呈现下降的趋势,而转动温度呈现上升的趋势。这些结果对研究宇宙星体和探索高温化学反应有重要作用。

In order to study the B^2Σ^+~X^2Σ^+ spectra of CN radical and temperature under different conditions, laser-induced breakdown spectroscopy was used to break high purity graphite in air environment and produce CN free radicals. Emission spectra of B^2Σ^+~X^2Σ^+ were measured by high resolution spectrometer. The spectra of CN radicals under different conditions were studied by changing laser energy and laser focus position. The results show that, when laser energy is tuned from 30mJ to 50mJ and the increasing step size is 5mJ, spectral intensity increases with the increase of laser energy. When single pulse energy is 50mJ, spectral intensity reaches its maximum. In addition, when the distance between the upper surface of graphite and laser focal point is 8mm, signal-to-noise ratio reaches the maximum. LIFBASE software is used to fit the spectral data. The vibration temperature of CN radical is about 10 4K. The rotating temperature is about 4000K. Vibration temperature of CN radicals decreases and rotational temperature increases with the increase of distance. These results play an important role in studying cosmic stars and exploring high temperature chemical reaction.