正交双脉冲诱导等离子体信号增强的理论研究,Journal of Analytical Atomic Spectrometry

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正交双脉冲诱导等离子体信号增强的理论研究
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2022-06-17 , DOI: 10.1039/d2ja00105e
Junxiao Wang _{1,

2} , Yang Zhao ₃ , Gang Wang ₄ , Lei Zhang _{1,

2} , Shuqing Wang ₅ , Wanfei Zhang ₄ , Xiaofei Ma ₄ , Zhenrong Liu ₄ , Xuebin Luo ₄ , Weiguang Ma _{1,

2} , Zefu Ye ₆ , Zhujun Zhu ₆ , Wangbao Yin _{1,

2} , Suotang Jia _{1,

2}

Affiliation

双脉冲技术通过耦合激光束增加了等离子体羽流与目标之间的能量传输，大大增强了信号，降低了激光诱导击穿光谱（LIBS）的检测限，提高了微量元素分析的能力。本文利用流体动力学模型从理论上研究了正交双脉冲LIBS（DP-LIBS）中等离子体的发射特性，包括脉冲间隔和第二激光脉冲光斑位置对各种物质发射强度的影响。在再加热模式。结果表明，在再加热模式下，双脉冲与单脉冲的最大强度比对应的脉冲间隔出现在0.2~0.5 μs，而在预消融模式下，它随着脉冲间隔的增加而增加。根据预消融模式下消融脉冲前样品上方背景气体数密度的降低，从等离子体-等离子体耦合效应和压力效应两个方面解释谱线强度的增强机制。此外，还探讨了这些模式下等离子体温度的空间分布和升高机制。结果表明，在再加热模式下，等离子体温度是通过直接吸收激光能量来提高的，而在预烧蚀模式下，是通过减少蒸气等离子体和气体等离子体之间的能量损失和削弱屏蔽作用来提高等离子体温度的。双脉冲等离子体的理论分析为DP-LIBS的实验研究和应用提供了理论依据。

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Theoretical study on signal enhancement of orthogonal double pulse induced plasma

The double pulse technology increases the energy transmission between the plasma plume and the target by coupling the laser beam, which greatly enhances the signal, reduces the detection limit of laser-induced breakdown spectroscopy (LIBS) and improves the ability of trace elemental analysis. In this paper, the emission characteristics of plasma in orthogonal double-pulse LIBS (DP-LIBS) are studied theoretically by using the hydrodynamics model, including the effects of pulse interval and spot position of the second laser pulse on the emission intensity of various species in the reheating mode. The results show that in the reheating mode, the pulse interval corresponding to the maximum intensity ratio of double pulse to single pulse occurs at 0.2–0.5 μs, while in the pre-ablation mode, it increases with the increase of pulse interval. According to the decrease of the number density of the background gas above the sample before the ablation pulse in the pre-ablation mode, the enhancement mechanism of spectral line intensity is explained from two aspects: plasma–plasma coupling effect and pressure effect. In addition, the spatial distribution and raising mechanism of plasma temperature in these modes are also explored. It shows that in the reheating mode, the plasma temperature is increased by directly absorbing laser energy, while in the pre-ablation mode, it is increased by reducing the energy loss between vapor plasma and gas plasma and weakening the shielding effect. The theoretical analysis of double pulse plasma provides a theoretical basis for the experimental research and application of DP-LIBS.

更新日期：2022-06-17

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