双飞秒激光脉冲诱导击穿光谱增强特性研究

在大气环境中，以钴为样品，通过单脉冲飞秒激光诱导击穿光谱及共轴双飞秒脉冲激光诱导击穿光谱的对比实验，研究了双脉冲激光诱导击穿光谱的谱线增强机制，测量了双脉冲激光诱导击穿光谱随脉冲时间间隔的变化趋势。结果表明，在最优化的脉冲时间间隔条件下，双脉冲激光诱导等离子体光谱获得明显增强。进一步，通过线性Boltzmann法得出了电子温度随脉冲时间间隔的演化，发现了谱线增强因子和电子温度随脉冲时间间隔呈现出相同的演化趋势，并经历两个明显的变化过程，得出了谱线信号强度的增强依赖于电子温度升高的结论。

Enhanced laser-induced breakdown spectroscopy on Co sample with double femtosecond laser pulses

This paper presents the study on the enhancement mechanism of laser-induced breakdown spectroscopy on cobalt sample with double femtosecond pulse. The double-pulse experiments were carried out in the collinear beam geometry in air. The influence of the delay between the two collinear laser pulses was investigated by changing the pulses path length. In cases of no delay between the two pulses, the laser-induced breakdown spectroscopy is equivalent to that induced by a single pulse laser with energy equals to the sum of the double collinear pulse energy. The obtained results show that with an optimized delay, the double-pulse laser-induced breakdown spectroscopy has a very clear enhancement comparing with the single-pulse laser induced breakdown spectroscopy. In addition, the dependence of the electron temperature obtained by linear Boltzmann method on the pulse interval was investigated. The experiment shows that the dependence of spectral enhancement factor on the pulse interval is the same as that of the electron temperature, both of them go through two obvious changing processes. Analysing by the Boltzmann equation, we draw the conclusion that the spectral signal enhancement depends on the electron temperature.