Laser-induced breakdown spectroscopy (LIBS) is a modern analytical technique emerging in recent years, which widely used in qualitative and quantitative determination of various samples. However, because the plasma spectral enhancement mechanism of the two typical LIBS technologies(pre-ablation and reheating LIBS) varies greatly, how to choose the spectral enhancement solution and rationally configure the LIBS system in different applications still needs further research and discussion. In this paper, we constructed a defocusing collinear dual-pulse LIBS(DP-LIBS) experimental system, and carried out relevant experiments for pre-ablation and reheating plasma spectral enhancement, and studied separately the effects of ablation sampling, reheating and re-excitation of plasma in collinear DP-LIBS. The experimental results show that the pre-ablation defocus collinear DP-LIBS is an indirect spectral enhancement technology, which uses the pre-ablation laser to change the surface environment of the sample, so that the sample is more conducive to the excitation of plasma, thus achieving spectral enhancement. The spectral and ablative crater analysis of the reheating defocus collinear DP-LIBS show that it enhances the spectral signal by reheating and re-exciting the plasma by the second laser beam, which is a direct spectral enhancement technology and has better enhancement effect than indirect enhancement technologies such as pre-ablation DP-LIBS. In addition, the laser inter-pulse delay time is an important factor in maintaining the temperature of the plasma to sustain the atomic radiation. Under different spectral enhancement solution, proper configuration of laser inter-pulse delay time is the key factor to obtain high spectral intensity and good signal-to-noise ratio.

激光诱导击穿光谱（LIBS）是近年来兴起的一种现代分析技术，广泛应用于各种样品的定性和定量测定。但是，由于两种典型LIBS技术（预烧蚀和再加热LIBS）的等离子体光谱增强机制差异很大，如何在不同应用中选择光谱增强方案和合理配置LIBS系统仍有待进一步研究和探讨。本文构建了离焦共线双脉冲LIBS(DP-LIBS)实验系统，并进行了预烧蚀和再加热等离子体光谱增强的相关实验，分别研究了烧蚀采样、再加热和再激发的影响。共线 DP-LIBS 中的血浆。实验结果表明，预烧蚀离焦共线DP-LIBS是一种间接光谱增强技术，它利用预烧蚀激光改变样品的表面环境，使样品更有利于等离子体的激发，从而实现光谱增强。再加热离焦共线DP-LIBS的光谱和烧蚀坑分析表明，它通过第二束激光对等离子体进行再加热和再激发来增强光谱信号，这是一种直接的光谱增强技术，比间接增强具有更好的增强效果技术，如预消融 DP-LIBS。此外，激光脉冲间延迟时间是维持等离子体温度以维持原子辐射的重要因素。在不同的光谱增强方案下，