Influence of Ar and O2 atmospheres on the Li atom concentration in the plasma produced by laser ablation of LiNbO3

Abstract

An analytic kinetic model is elaborated to determine the spatial evolution of the concentration of ground and excited Li atoms (up to the 3 2D level) present in the plasma generated by pulsed laser ablation of a LiNbO3 crystal in gas atmospheres (at 1 Torr) of different nature, both reactive (O2) and inert (Ar). Whereas the Li atom population densities in the plasma produced in gas are, in general, higher than those found in vacuum, the concentration of ground Li atoms close to the substrate is similar in vacuum and Ar, though lower than in O2. It is suggested that the reabsorption of radiation by the plasma is more important within O2 than in Ar since the absorber (ground Li) concentration is higher in O2 environments. A very reasonable qualitative agreement is found when comparing the Li I-670.8 nm spectral line emission intensity predicted by the model with that obtained experimentally in Ar and O2 atmospheres.