Temporal and spatial evolution of the electronic density and temperature of the plasma produced by laser ablation of LiNbO₃

Abstract

Emission spectroscopy is used to determine the spatial and temporal evolution of the electronic temperature (Te) and density (Ne) of the plasma generated by laser ablation in vacuum of a LiNbO₃ target. It is found that whereas Ne (in the range of 10¹⁶ cm⁻³) decreases by a factor of 2 as the distance to the target surface increases 10 mm, Te (in the range 0.7–0.8 eV) only decreases 10% between 2 and 4 mm from the target to remain nearly constant for longer distances. While Te is almost constant in time at the studied distances, Ne presents a maximum at a time delay that increases when increasing the distance to the target surface. The space–time constancy of Te is related to a collisional decoupling of the heavy species in the plasma for distances longer than 2–4 mm.