微波探针对叶菜激光诱导击穿光谱信号增强效果的影响

Effect of Microwave Probes on Enhancement of Laser-Induced Breakdown Spectral Signal of Leaf Vegetable

微波产生形式会影响激光诱导击穿光谱(LIBS)中等离子体光谱信号的强度和稳定性。实验选择重金属镉(Cd)质量分数为1.5×10^(-5)的叶菜样品作为研究对象,对比分析了双针、单针、环形、双环4种微波探针和前、中、后3个探针位置处传导微波对等离子体光谱信号强度和稳定性的影响,以优化微波辅助LIBS(MA-LIBS)实验中的微波作用形式,达到更好的辅助增强效果。分析MA-LIBS光谱图发现,Cd元素的等离子体光谱信号增强了2.58倍,Si、P元素的等离子体光谱信号强度分别增强了2.70倍和3.08倍,有较好的增强效果。这表明:选择合适形状的微波探针和微波加载位置可以提高微波辅助增强效果,增强LIBS技术在低浓度样品检测方面的应用性能。

The methods that are used to produce microwaves can affect the strength and stability of plasma spectral signal in laser-induced breakdown spectroscopy （LIBS）. LeaF vegetables that contain cadmium （Cd） at mass fraction of 1.5× 10-5 are used as the subjects of this study. The influences of microwave probe with four shapes, such as the single-needle, double-needle, single-ring, and double-rings microwave probes, are studied. The three microwave loading positions, which include the front, middle, and end of the probes, are also investigated. The form of microwave function in the microwave assisted LIBS （MA-LIBS） experiment is optimized to achieve better auxiliary enhancement effect. After analyzing the spectral lines of the MA-LIBS, we find that the plasma spectral signal of Cd element is increased by 2.58 times, whereas Si and P elements is increased by 2.70 and 3.08 times, respectively. Suitable microwave probe shapes and loading positions can improve the effects of microwave-assisted enhancement, which further improves the performance of the LIBS technology in the application fields.