采用波长1064 nm的调Q脉冲Nd:YAG激光器和多通道小型光纤光栅光谱仪,搭建了一套激光诱导击穿光谱分析系统。选择土壤中常 见元素AlⅡ(422.68 nm)作为分析线,详细研究激光能量和采样延迟对激光诱导土壤等离子体光谱特性的影响。在相同激光能量下,随着 采样延迟时间增加,信号强度、背景强度、噪声都将减弱,而信噪比则呈现先增大后减小的趋势;在相同采样延迟时间下,增加激光能量, 信号强度、噪声也将增强,而背景强度和信噪比的变化则呈现先增加后减小的趋势。对于某一特定的激光能量, 存在一个与之相对应的 最佳采样延迟时间,随着激光能量增加,最佳延迟时间也会增大。综合考虑采样延迟时间和激光能量对激光诱导等离子体光 谱信噪比的影响,给出了系统的最优化工作参数是激光能量120 mJ、最佳采样延迟时间1.5 μs。

A laser induced breakdown spectroscopy analytical system was established by using a pulsed 1064 nm Nd:YAG laser and a portable fiber optical spectrometer. The emitted spectra of the laser induced soil plasma were recorded along with the variation of experimental parameters. By using the AlⅡ 422.68 nm as the analysis line, the effects of the laser energy and data acquisition delay time on the spectrum characterizations of soil plasma emission were investigated in detail. Generally, at a fixed laser energy, the signal intensity, background and noise of the spectrum decrease with a longer acquisition time delay, while the signal to noise ratio (SNR) first increases to a maximum and then decreases. And at a fixed data acquisition time delay, the signal intensity and noise of the spectrum increase with the increase of laser energy, but the background and SNR first increase to a maximum and then decrease. For specific laser energy, the SNR can be optimized at a selected suitable data acquisition time delay, and the optimal time delay will increase with increased laser energy. Based on the combination effects of laser energy and data acquisition time delay, the optimized parameters of the system are 120 mJ for the laser energy and 1.5 μs for the acquisition delay time.