Role of Al–O2 chemistry in the laser-induced vaporization of Al films in air

Evidence for the prominent role of atypical reactions, and enhanced vaporization arising from resonant optical absorption of the exciting beam, in the pulsed-laser heating of thin films is presented. Time-resolved emission of Al and the reaction product AlO are monitored in the laser vaporization of Al films in air. Optical emission is observed up to 200 microseconds after an 8 μs heating pulse, indicative of long chemical lifetimes. Furthermore, increased emission from both Al and AlO up to 100 μs after the heating pulse, are observed when the laser wavelength is tuned to resonance with AlO transitions. Since the electronic resonance with the reaction product AlO affects the subsequent emission of Al, these measurements underscore the importance of physical and chemical processes peculiar to laser-induced vaporization, and ablation.