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激光诱导等离子体发射光谱,研究了激光输出能量(100～500 mJ)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背比.当激光束被适当散焦以后激发样品时,能够进一步改善光谱质量,散焦位置为+6mm时元素Mg,Al,K和Fe的谱线强度比未散焦时分别提高了46％,63％,59％和45％,而光谱信背比分别提高了11％,31％,35％和38％.这为检测土壤样品中痕量杂质元素奠定了基础.%To improve the quality of laser-induced breakdown spectroscopy, nanosecond pulse laser generated by Nd : YAG laser was used to excite soil sample. The laser-induced plasma spectrum was observed using a grating spectrometer and a photoelectric detection system. The influence of laser output energy ranging from 100 to 500 Mj on the radiation intensity of plasma was studied. The results show that both the line intensity and signal-to-background ratio can be enhanced under the optimized condition that the laser energy is 200 Mj . The quality of spectrum was further improved after the laser beam used to excite the sample was defocused properly. When the defocusing position is +6 mm, the spectral lines intensity of element Mg, Al, K and Fe increased about 46%, 63%, 59% and 45% compared to that without defocusing respectively. The spectral signal-to-background ratio increased about 11%, 31%, 35% and 38% respectively. This lays a foundation for detection of trace impurity element in soil.
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