Atomic hydrogen and molecular carbon emissions in laser-induced breakdown spectroscopy

Abstract

This article addresses hydrogen Balmer series measurements following laser-induced optical breakdown. Electron density on the order of 1 × 1025 m-3 can be inferred using Hα Stark width and shift for plasma generated in 1 to 1.3 × 105 Pa, gaseous hydrogen. The Hβ line can be utilized for electron density up to 7 × 1023 m-3. Laser ablation of aluminium reveals limits of application of the Balmer series. Electron excitation temperature is inferred utilizing Boltzmann plot techniques that include Hα, Hβ and Hγ atomic lines. Hβ and Hγ lines show presence of molecular carbon in a 2.7 and 6.5 × 105 Pa, expanding methane flow. Occurrence of superposition spectra in the plasma decay due to recombination or due to onset of chemical reactions necessitates consideration of both atomic and molecular emissions following laser-induced optical breakdown.