双脉冲激光诱导土壤等离子体光谱实验研究

摘要

采用波长分别为532 nm 和1064 nm 的 Nd－YAG 脉冲激光器作为光源，以中阶梯光栅光谱仪和增强型电荷耦合器件（ICCD）作为光谱采集和检测器件，分析了激光脉冲间隔和积分延时对土壤中 Pb 元素激光诱导击穿等离子体发射光谱的影响。实验结果表明：双脉冲激光激发的等离子体谱线强度较单脉冲有整体的提升，在0～－20μs 的脉冲间隔区间内谱线强度存在一个峰值，当脉冲间隔为－15μs 时，Pb 元素等离子体谱线增强效果最好；不同脉冲间隔的等离子体发射谱线强度都随积分延时的增加呈衰减趋势，脉冲间隔越大，衰减速率越快，通过对 Pb 元素等离子体谱线强度与积分延迟的指数曲线拟合，得到脉冲间隔－5μs 的双脉冲 LIBS 等离子体谱线衰减时间约为－15μs 的1．5倍。%The Nd-YAG pulse lasers with wavelength of 532 nm and 1 064 nm are used as excitation source, and with the echelle spectrometer and intensity charge-coupled device (ICCD) as the spectral acquisition and detection devices, an analysis is made of the influence laser pulse interval and integral time delay on Pb element laser induced breakdown plasma emission spectrum in soil.The experimental results show that the plasma spec-tral line intensity excited by double-pulse laser has an overall lift compared with single pulse, the spectral line intensity has a peak in 0 ~-20μs pulse interval range, when the pulse interval is -15μs, Pb element plasma spectral enhancement effect is best; the plasma emission spectral line intensity of different pulse interval shows a attenuation trend with the increase of the integral time delay, the bigger the pulse interval, the greater the atten-uation rate.Based on the index curve fitting of Pb element plasma spectral line intensity and integral delay, the double-pulse LIBS plasma spectrum attenuation time of -5μs pulse interval is is obtained and is about 1.5 times to -15μs pulse interval.