Abstract The enhanced laser induced breakdown spectroscopy is highly desirable for the quantitatively detection with low limit of detection (LOD) and high accuracy. Higher enhancement factor is always obtained from discharge assisted laser-induced breakdown spectroscopy with enough higher energy injection in comparison to the normally standard laser induced breakdown spectroscopy (LIBS), which means dangerous with high voltage and elevated power. Here, a low power (10 W) injected unipolar discharge arc is proven to greatly enhance the LIBS with a large enhancement factor up to 13.8 when the discharged electric arc followed by a laser induced plasma are simultaneously applied on a silicon wafer, which is comparative or larger than those results with high-power (kW) and high voltage (kV) being applied. Furthermore, the enhanced technique is applied on an actual qualitative detection of cadmium in soil. The lines of Cd II (214.44 nm) from soil is enhanced as compared to a LIBS measurement. Accordingly, the LOD of the typical emission line is reduced to 23.5 ppm by the unipolar discharge arc assisted laser induced breakdown spectroscopy (UD-LIBS), which is 2.45-fold lower than that from the normal LIBS. The pre-ionization of the environment and the surface by the modulated discharge arc to directly make the Inverse Bremsstrahlung (IB) absorption with higher absorption coefficient dominate the initial stage of plasma formation rather than the multi-photon absorption process, thus make both electron density and the temperature of plasma raising are the main mechanism of spectral enhancement, which is further proved by the evolution dynamics images of two plasma overlapping processes under an in-situ intensified charge-coupled device (ICCD) based photographic system. The simple, portable, commercial highly enhancement way is greatly benefit to the actual applications.

中文翻译：

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低功率单极放弧辅助激光诱导等离子体光谱中的高增强因子

摘要 增强型激光诱导击穿光谱是低检测限（LOD）和高精度定量检测的理想选择。与通常标准的激光诱导击穿光谱 (LIBS) 相比，放电辅助激光诱导击穿光谱具有足够高的能量注入，总是可以获得更高的增强因子，这意味着高压和高功率的危险。在这里，当放电电弧和激光诱导等离子体同时施加在硅晶片上时，低功率（10 W）注入单极放电弧被证明可以极大地增强 LIBS，增强因子高达 13.8，这是比较或大于应用高功率 (kW) 和高电压 (kV) 的结果。此外，增强技术应用于土壤中镉的实际定性检测。与 LIBS 测量相比，来自土壤的 Cd II (214.44 nm) 谱线得到增强。因此，典型发射线的 LOD 通过单极放电弧辅助激光诱导击穿光谱 (UD-LIBS) 降低到 23.5 ppm，比普通 LIBS 低 2.45 倍。通过调制放电弧对环境和表面进行预电离，直接使吸收系数较高的逆轫致辐射（IB）吸收主导等离子体形成的初始阶段而不是多光子吸收过程，从而使电子密度和等离子体温度升高是光谱增强的主要机制，在基于原位增强电荷耦合器件 (ICCD) 的照相系统下，两个等离子体重叠过程的演化动力学图像进一步证明了这一点。这种简单、便携、商业化的高度增强方式对实际应用大有裨益。