Influence of spark discharge on Al(i) and AlO spectra in femtosecond laser-induced aluminum plasmas

Abstract

In this study, the influence of spark discharge on Al(I) and AlO emission intensities in laser-induced breakdown spectroscopy (LIBS) is investigated experimentally. A femtosecond pulsed laser is used to excite an aluminum sample and produces aluminum plasma between the sample surface and a discharge electrode. The plasma triggers high-voltage spark discharge (SD), enhancing the spectral intensity of the aluminum plasma. The emission of Al atomic lines and AlO bands in the case of the SD is stronger than that in the case using femtosecond LIBS alone. And the spectral intensities of Al(I) lines increase continuously as the discharge voltage increases from 0 kV to 2.0 kV, while AlO molecular emission first increases and then almost remains unchanged. Finally, the vibration temperature of the AlO radical is calculated by fitted AlO emission data, and the vibration temperature of the AlO radical hardly changes with the increase of the discharge voltage. The results indicate that the atomic spectral intensity is sensitive to the discharge voltage, but not the molecular band emission in femtosecond LIBS.