Spatiotemporal diagnostics of laser induced plasma of potassium gallosilicate zeolite

Abstract

The present work focuses on the analysis of laser induced plasma of a zeolite sample to study its spatial and temporal evolution. Plasmas were induced by focusing a high-peak power IR CO₂ pulsed laser at 10.6 μm and irradiance 6.3 GW cm⁻² onto a sample under 0.01 Pa vacuum, which produced special conditions allowing the detection of species in high ionization states and velocities. In this study, high spatial, temporal and spectral resolution was obtained using imaging by an optical emission spectroscopy method, namely, laser induced breakdown spectroscopy. In addition, this work introduces the possibility of studying the early stages of plasma evolution. The induced plasma shows electronically excited neutral K, Ga, Si and O atoms and ionized K⁺, Ga⁺, Ga²⁺, Si⁺, Si²⁺, Si³⁺, O⁺, O²⁺, and O³⁺ species. Time-resolved two-dimensional spectra, which were also spatially resolved, were used to study the expanded distribution of some species ejected during ablation. Spatial and temporal variations of different atoms and excited ionic species are reported. Decreasing electron densities in the order of 10¹⁷ to 10¹⁶ cm⁻³ at 2 mm from the target surface were measured using Stark broadening in the plasma lifetime of 4 μs. The measured temperature range of electrons is 35 000 to 5800 K within the first 5 μs after initiation of optical breakdown and for the supposed local thermodynamic equilibrium of the plume at a distance of 2 mm from the target.