Characterization study of laser induced breakdown spectroscopy on submerged nickel target

Abstract

Laser Induced Breakdown Spectroscopy (LIBS), as an in-situ, real time, multi-element analysis tool, has been used in many applications. While for oceanic applications, many difficulties arise due to lower ablation efficiency and shorter emission lifetime of LIBS in water. The complexity of ocean environment makes LIBS performance even worse. To evaluate the potential using of LIBS for oceanic application, extensive experimental investigations of LIBS have been carried out with a nickel sample submerged in water under both single pulse and dual-pulse laser ablation. It was found that, for short duration laser pulse ablation, the continuum emission lifetime was nearly equal to the duration of laser pulse, with nickel atomic emission hardly appeared. As the laser pulse duration going up to 50 ns, several nickel atomic lines were turned up on the continuum background. With dual-pulse laser ablation, the intensity of theses nickel atomic lines were enhanced significantly, which demonstrated that dual-pulse had better LIBS performance. The LIBS signals of nickel target within the wavelength range of 330nm-390 nm were obtained under dual-pulse laser ablation. And severe self-absorption phenomenon was observed among those nickel atomic emission lines. The possible reason for self-absorption has been discussed and was attributed to the relevant transmission energy levels. To verify the effect of cations in water, LIBS investigation was carried out with the nickel target submerged in Na+, K+ solution or deep-sea water. It was found that both intensity and signal to background ratio had been improved with the cations in water. All those obtained results suggested that LIBS had great potential to be used in oceanic application.