预烧蚀双脉冲激光诱导Fe等离子体发射光谱的实验研究

Experimental Investigation on Pre-Ablation Dual-Pulse Laser-Induced Fe Plasmas

采用预烧蚀双脉冲激光诱导击穿光谱(DP-LIBS)技术对Fe元素的发射光谱开展实验研究。通过比较单脉冲(SP)和双脉冲(DP)激发的等离子体光谱,发现采用预烧蚀DP烧蚀样品可以提高光谱信号的强度;以预烧蚀DP-LIBS信号的增强程度为对象,研究光谱增强程度随两束激光脉冲间隔在-102～0μs的变化,发现两脉冲间隔为-9μs时,Fe原子谱线的增强程度最大,信号增强了6.5倍。谱线半峰全宽(FWHM)的变化反映了电子密度的变化,实验研究并分析了谱线FWHM随两脉冲间隔和采集延时的变化。对增强程度随延时的变化进行研究,发现两脉冲间隔不同,增强程度随采集延时的变化也不同。

Pre-ablation double-pulse （DP） is applied to induce Fe plasmas, and the emission spectrum is investigated. Spectra intensities are compared using single-pulse laser-induced breakdown spectroscopy （SP-LIBS） and pre-ablation double-pulse laser-induced breakdown spectroscopy （DP-LIBS）. The signal intensity is enhanced largely by pre-ablation DP-LIBS excitation compared to SP-LIBS. Signal enhancement acts as object of study. The influence of the delay between the two laser pulses （ 102-0 μs） is investigated, and enhancement reaches maximum at -- 9 μs, and 6.5 times enhanced signal is observed in atomic line. Electron density is reflected by spectral line of full width at half maximum （FWHM）. FWHM is studied with the delay between the two laser pulses and the gate delay time. A correlation between the increases in emission lines intensities and the gate delay time is established in pre-ablation DP approach. Difference of the delay between the two laser pulses, intensity enhancement versus the gate delay time is different.