PRE-ABLATION SPARK; ORTHOGONAL BEAM GEOMETRY; INDUCED PLASMAS; CONFIGURATION; SPECTROMETRY; EMISSION; MATRICES; SINGLE; LIBS

Two Q-switched Nd: YAG lasers at 1064-nm wavelength have been employed to detect the trace elements in microalloy steel samples by single-pulse and reheating double-pulse laser-induced breakdown spectroscopy. It is found that the emission lines intensities of the trace elements were significantly enhanced by reheating double-pulse scheme. Furthermore, the extent of the enhancement of the line intensity was related to the excitation energy level of the emission line. Then, the emission enhancement was explained by the investigation of the spatial resolution of the plasma temperatures. The results have shown that the enhancement mechanism can be attributed to the greater and hotter plasma generated by the re-excitation of the reheating laser pulse in double-pulse scheme. Finally, calibration plots were constructed for Mn, Cr, and Cu using a set of certified microalloy steel samples. The detection limits of the trace elements were calculated for the reheating double-pulse scheme and compared to those of single-pulse scheme. It has been shown that the detection limits of the trace elements were improved by a factor of 1.81-3.46 when the reheating double-pulse scheme was used.