激光诱导击穿空气等离子体时间分辨特性的光谱研究

Spectroscopic study on the time evolution behaviors of the laser-induced breakdown air plasma

空气等离子体的时间行为对空气环境下激光诱导等离子体形成过程的研究有重要意义.本文将纳秒Nd:YAG脉冲激光(1064 nm)聚焦于一个大气压的空气中,诱导其产生等离子体.利用具有纳秒时间分辨功能的PI-MAX-II型ICCD,采用时间分辨光谱方法,研究了大气环境下激光诱导等离子体的时间行为.大气环境下的激光诱导等离子体光谱广泛分布于300—900 nm范围内,并且是由带状光谱和线状光谱叠加而成的.根据美国国家标准与技术研究院原子发射谱线数据库,对等离子体光谱中的氧、氮、氢等元素的特征谱线进行了识别和归属.给出了激光诱导击穿大气等离子体光谱随时间演化的直观图像,根据空气等离子体发射谱线计算了等离子体电子温度和等离子体电子密度.这些结果对于提高在大气环境下进行的在线测量结果的准确性和精确性具有重要的科学意义.

The time-resolved spectra of the air-breakdown plasma generated by the nanosecond pulsed 1064 nm beam of a Nd ： YAG laser are investigated by using a PI-MAX-II ICCD with nano-time-resolved features. The results show that the laser-induced plasma spectrum in atmospheric environment is widely distributed in a range of 300-900 nm, and it is superimposed by continuous spectra and sharp line spectra. The spectral lines of oxygen, nitrogen and hydrogen are identified according to the National Institute of Standards and Technology database of atomic emission. The intuitive figures of laser-induced breakdown atmospheric plasma spectra with time resolution are given. The electron temperature and electron density are calculated according to the emission spectra. The results have scientific significance for improving the accuracy and precision of the on-line measurement in the atmospheric environment.