Micro-destructive analysis with high sensitivity using double-pulse resonant laser-induced breakdown spectroscopy

To achieve micro-destructive analysis with high sensitivity, single beam splitting and an appropriate optical geometric configuration were used to establish a double pulse resonant laser-induced breakdown spectroscopy (DP-RLIBS) system. A wavelength-tunable laser was divided into reflection and transmission beams by using a beam splitter; the reflected laser pulse was firstly used to ablate the sample (similar to the front edge of the pulse in RLIBS), and then the transmission laser pulse was used to resonantly excite the target atoms in the vapor plume (similar to the rear edge of the pulse in RLIBS), which was equivalent to the time spent on abating the sample and resonant excitation of the target elements was increased, resulting in an evidently increasing number of ablated target atoms in the plasma and a more sufficient energy for resonant excitation. A detailed comparison of the spectral stability, sensitivity and micro-destructive detection performance of DP-RLIBS and RLIBS for lead (Pb) in copper alloys was conducted. An obvious signal enhancement was observed using DP-RLIBS. The calibration curves of Pb I 405.78 nm in DP-RLIBS and RLIBS were established. The coefficient of determination R² in DP-RLIBS was 0.992, higher than that of 0.947 and 0.859 with RLIBS-1 and RLIBS-2, respectively. The 3σ-limit of detection (LoD) for Pb in copper alloys was 9 ppm with DP-RLIBS, lower than the best value of 29 ppm with RLIBS, and the ablation crater radius was 66 μm, which was basically the same as 62 μm of RLIBS. The results demonstrated the capability of DP-RLIBS for sensitivity improvement and micro-destructive detection in LIBS technology.