[Comparative Study on Laser Induced Breakdown Spectroscopy Based on Single Pulse and Re-Heating Orthogonal Dual Pulse].

In order to improve the detection sensitivity and spectral characteristic of laser-induced breakdown spectroscopy (LIBS), re-heating orthogonal dual-pulse configuration is adopted to analyze Fe, Pb, Ca and Mg contained in the sample and soil sample contained different concentrations of heavy mental Cr. Variation relationship between spectral intensity, signal-to-background(SBR) of four characteristic spectral lines FeⅠ：404.581 nm，PbⅠ：405.78 nm，CaⅠ：422.67 nm and MgⅠ：518.361 nm and time interval of two laser pulses is discussed, the best time interval of two laser pulses is obtained 1.0 μs. In the condition of single pulse and dual-pulse, the enhancement factor of spectral intensity of four characteristic spectral lines FeⅠ：404.581 nm，PbⅠ：405.78 nm，CaⅠ：422.67 nm and MgⅠ：518.361 nm is respectively 2.23，2.31，2.42 and 2.10; The time evolution characteristic of spectral intensity of characteristic spectral lines FeⅠ：404.581 nm and CaⅠ：422.67 nm is considered, and also the variation relationship between spectral acquisition delay time and SBR of four characteristic spectral lines, dual-pulse can prolong decay time of spectral intensity and improve the SBR of characteristic spectral lines; time evolution characteristic of plasma temperature and electron density is compared in the condition of single pulse and dual-pulse, maximum elevation of plasma temperature is found to be 730 K, and the maximum increase of electron density is 1.8×1016 cm-3. The limits of detection of heavy mental Cr are obtained 38 and 20 μg·g-1 respectively in condition of single and double pulse, limit of detection of Cr is reduced approximately 2 times by the condition of re-heating orthogonal dual pulse. Results above indicate that re-heating orthogonal dual-pulse can improve detection sensibility and spectral characteristic of LIBS technique, which provides an effective method for decreasing the limit of detection of elements.