RESUMO
The combination of femtosecond laser filament ablation and emission spectroscopy is a potential analytical tool for standoff characterization of samples of interest. We compare the emission features and physical conditions of plasmas generated from metal targets using either by loosely focused femtosecond filaments or by lens-free filaments. Our results show that the filament generation conditions influence the plasma properties appreciably which include the atomic and molecular emission features, persistence and plasma fundamentals (temperature and density). The loosely focused fs pulse filaments are found to generate ablation plumes with higher temperature and density along with increased persistence compared to plumes generated by lens-free filaments.
RESUMO
Ultrafast laser filament induced breakdown spectroscopy is a very promising method for remote material detection. We present characteristics of plasmas generated in a metal target by laser filaments in air. Our measurements show that the temperature of the ablation plasma is clamped along the filament channel due to intensity clamping in a filament. Nevertheless, significant changes in radiation intensity are noticeable, and this is essentially due to variation in the number density of emitting atoms. The present results also explain the near absence of ion emission but strong atomic neutral emission from plumes produced during fs LIBS in air.
