为了研究液体中重金属元素的双脉冲激光诱导击穿光谱,通过双脉 冲激光诱导击穿光谱(Double pulse laser induced breakdown spectroscopy, DP-LIBS)技术, 对竖直流动的CuSO4 水溶液样品中Cu元素激光诱导击穿光谱的特性进行测量和分析。 实验中使用两台532 nm Nd:YAG激光器作为激发光源,等离子体信号通过光栅光谱仪和CCD进行采集。实验考察了DP-LIBS积分延时、 激光脉冲间隔等参数对LIBS信号的影响。研究结果表明Cu元素双脉冲激发时的等离子体特征谱线发射强度 是单脉冲激发时特征谱线发射强度的2倍左右,信噪比约为3.3倍,当两束激光脉冲间隔2～3μs时, 谱线发射强度有最大增强,最后由定标曲线拟合结果得到Cu元素在双脉冲检测限为9.87 mg/L,比单脉 冲LIBS提高了约6倍,实验结果为双脉冲LIBS技术应用于水体中重金属快速检测提供了依据。

In order to study the heavy metal elements in liquid by double pulse laser induced breakdown spectroscopy, double pulsed laser induced breakdown spectroscopy (DP-LIBS) was used, the LIBS characteristics of Cu elements in a vertical flow of aqueous solution of CuSO4 were measured and analyzed. Two Q-switched Nd:YAG lasers operating at 532 nm was utilized to generate plasma on a flowing liquid surface, and plasma signal by detecting the CCD grating spectrometer. The gate delay, the delay time between two lasers of DP-LIBS were investigated experimentally. The results show that the intensity and SNR of Cu emission lines excited by double pulse is about 2 and 3.3 times than the intensity of line emission excited by the single pulse separately. When the delay time between two lasers at 2～3μs, emission line intensity reached maximum enhancement. The detection limit of metal ion in water solution under the optimized operation conditions was found to be 9.87 mg/L for Cu, which is about 6 times than single pulse. The results provide a basis for rapid detection heavy metals in water solution using DP-LIBS technique.