摘要:
为了改善激光诱导击穿光谱质量，采用Nd:YAG激光器输出的纳秒脉冲激光激发土壤样品，由光栅光谱仪和光电检测系统记录等离子体发射光谱，研究了激光输出能量（100~500 mJ）和NaCl样品添加剂（质量分数0%~20%）对等离子体辐射强度的影响。实验结果表明，在激光能量为200 mJ的优化条件下，可以提高光谱强度和信噪比，而更高激光能量诱导的等离子体中光谱线自吸严重。当土壤样品中加入适量NaCl添加剂以后，能够进一步改善激光光谱质量。NaCl加入量为10%时，等离子体中元素Fe,Ba,Al和Ti的谱线强度比无添加剂时分别提高了37%，32%， 32% 和70%，光谱信噪比分别提高了33%，26%，16% 和38%。而样品烧蚀量、电子温度和电子密度比无添加剂时分别提高了14%,9.6%和26%。
Abstract:
To improve the quality of laser-induced breakdown spectroscopy, the nanosecond pulse laser generated by Nd:YAG laser was used to excite soil samples. The plasma spectrum was observed using a grating spectrometer and a photoelectric detection system. The influence of laser output energy ranging from 100 mJ to 500 mJ and NaCl additive content ranging from 0% to 20% on the radiation intensity of plasma was studied. The experimental results show that both the line intensity and the signal-to-background ratio can be enhanced under the optimized condition that the laser energy is 200 mJ, and further increase of laser energy generates serious self-absorption effect in the laser-induced plasma. However, further improvement of spectrum quality was observed with adding proper amount of NaCl additive into the soil sample. For instance, when the content of NaCl additive is 10%, the spectral line intensities of elements Fe, Ba, Al and Ti increase around 37%, 32%, 32% and 70% than those without additive; the spectral signal-to-background ratios increase about 33%, 26%, 16% and 38%; while the ablation mass, electron temperature and electron density of plasmas go up 14%, 9.6% and 26%, respectively.
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