用激光感生击穿光谱对大气进行定量分析

Quantitative analysis of atmosphere by laser-induced breakdown spectroscopy

研究将激光感生击穿光谱技术用于元素定量分析的可行性。利用Nd：YAG激光器发出的激光与一个大气压下的空气相互作用产生激光等离子体，等离子体的光经单色仪分光后转化为电信号进入计算机，存储了600～800nm的等离子体光谱数据。利用自由定标模型对等离子体进行了分析。在延迟时间8μs、采样门宽0．4μs时，利用二维波尔兹曼平面得到了大气等离子体处于局部热平衡时的温度（1．62×10K）。在假设空气全部由N和O组成的条件下由自由定标模型得到了空气中氧的含量（20．75%）和氮的含量（79．25％）。试验结果与实际吻合得很好。实验证实了用激光感生击穿光谱对大气进行定量分析是可行的，为大气污染监测研究和试验工作奠定了基础。

In order to investigate the feasibility of quantitative analysis with laser-induced breakdown spectroscopy, plasmas were produced by a Q-switched Nd ： YAG laser interacted with the air at atmospheric pressure, then the light of plasmas entered the monochrometer and transferred into an electric signal, and the spectra of these plasmas in the range of 600-800 nm were stored and analyzed by the calibration-free model. Under the condition of delay time of 8 μs and gating pulse of 0.4 μs, the temperature of plasmas, which was in local thermal equilibrium （LTE）, was 1. 62× 10 K which was obtained by means of the two-dimensional Boltzmann plane. The 20.75% oxygen content and 79.25 nitrogen content in air were detected on the assumption that there were only oxygen and nitrogen constituents in the air. The results coincide well with the fact. The feasibility was validated by the experiment, and it built a strong basis for the further study and experiment of air pollutant monitoring.