Evaluation of gases' molecular abundance ratio by fiber-optic laser-induced breakdown spectroscopy with a metal-assisted method

A metal-assisted method is proposed for the evaluation of gases’ molecular abundance ratio in fiber-optic laser-induced breakdown spectroscopy (FO-LIBS). This method can reduce the laser ablation energy and make gas composition identification possible. The principle comes from the collision between the detected gases and the plasma produced by the laser ablation of the metal substrate. The interparticle collision in the plasma plume leads to gas molecules dissociating and sparking, which can be used to determine the gas composition. The quantitative relationship between spectral line intensity and molecular abundance ratio was developed over a large molecular abundance ratio range. The influence of laser ablation energy and substrate material on gas quantitative calibration measurement is also analyzed. The proposed metal-assisted method makes the measurement of gases’ molecular abundance ratios possible with an FO-LIBS system.