The long–short double-pulse laser-induced breakdown spectroscopy (LS-DP-LIBS) method was applied to qualitative and quantitative analyses of underwater steel samples to improve the detection ability of underwater measurement. The stable plasma intensity and discrete emission lines were detected using LS-DP-LIBS when comparing the measured results of single-pulse LIBS (SP-LIBS) and LS-DP-LIBS. The long pulse produces a cavitation bubble without plasma, and the short pulse induces the plasma of steel samples within the bubble. The detection features of LS-DP-LIBS for underwater steel samples were discussed in different intra-pulse delay time, long-pulse width, and delay time conditions when analyzing the measured spectra, the signal intensity of Fe(I) at 400.524 nm and 402.187 nm, Mn(I) at 404.136 nm, and intensity ratio of Mn(I) 404.136 nm/Fe(I) 402.187 nm. The results indicated that the plasma stability and spectral signal intensity were improved significantly with a long-pulse width of 80 µs in the intra-pulse delay time of 70 µs, which were appropriate for bubble formation and plasma generation. According to the discussion of the delay time effect, the state of generated plasma was almost stable from 650 ns to 850 ns. Manganese (Mn) contents in steel samples were analyzed quantitatively when measuring five steel samples with different Mn contents using LS-DP-LIBS in optimal experimental conditions. A strong linear dependence was observed with R²=0.9842, which demonstrated the feasibility and appropriateness of quantitative analysis for underwater measurement using LS-DP-LIBS.

将长短双脉冲激光诱导击穿光谱（LS-DP-LIBS）方法应用于水下钢样品的定性和定量分析，以提高水下测量的检测能力。在比较单脉冲 LIBS (SP-LIBS) 和 LS-DP-LIBS 的测量结果时，使用 LS-DP-LIBS 检测到稳定的等离子体强度和离散的发射线。长脉冲产生没有等离子体的空化气泡，短脉冲在气泡内诱发钢样品的等离子体。讨论了LS-DP-LIBS在不同脉冲内延迟时间、长脉冲宽度和延迟时间条件下对水下钢样品的检测特性，分析测量光谱、Fe(I)在400.524 nm处的信号强度和402.187 nm，404.136 nm 处的 Mn(I)，以及 Mn(I) 404 的强度比。136 nm/Fe(I) 402.187 nm。结果表明，等离子体稳定性和光谱信号强度显着提高，长脉冲宽度为 80 µs，脉冲内延迟时间为 70 µs，适合气泡形成和等离子体产生。根据延迟时间效应的讨论，产生的等离子体的状态在 650 ns 到 850 ns 之间几乎是稳定的。在最佳实验条件下使用 LS-DP-LIBS 测量具有不同 Mn 含量的五个钢样品时，对钢样品中的锰 (Mn) 含量进行了定量分析。观察到强烈的线性相关性 适用于气泡形成和等离子体生成。根据延迟时间效应的讨论，产生的等离子体的状态在 650 ns 到 850 ns 之间几乎是稳定的。在最佳实验条件下使用 LS-DP-LIBS 测量具有不同 Mn 含量的五个钢样品时，对钢样品中的锰 (Mn) 含量进行了定量分析。观察到强烈的线性相关性 适用于气泡形成和等离子体生成。根据延迟时间效应的讨论，产生的等离子体的状态在 650 ns 到 850 ns 之间几乎是稳定的。在最佳实验条件下使用 LS-DP-LIBS 测量具有不同 Mn 含量的五个钢样品时，对钢样品中的锰 (Mn) 含量进行了定量分析。观察到强烈的线性相关性R ² =0.9842，证明了使用LS-DP-LIBS进行水下测量定量分析的可行性和适用性。