Dynamics of molecular emission features from nanosecond, femtosecond laser and filament ablation plasmas

Abstract

The evolutionary paths of molecular and nanoparticle formation in laser ablation plumes are not well understood due to the complexity of numerous physical processes that occur simultaneously in a transient laser-produced plasma system. It is well known that the emission features of ions, atoms, molecules and nanoparticles in a laser ablation plume strongly depend on the laser irradiation conditions. We report the temporal emission features of AlO molecules in plasmas generated using a nanosecond laser, a femtosecond laser and filaments generated from a femtosecond laser. Our results show that, at a fixed laser energy, the persistence of AlO is found to be highest and lowest in ns and filament laser plasmas respectively while molecular species are formed at early times for both ultrashort pulse (fs and filament) generated plasmas. Analysis of the AlO emission band features show that the vibrational temperature of AlO decays rapidly in filament assisted laser ablation plumes.