Dynamics of excimer laser-ablated aluminum neutral atom plume measured by dye laser resonance absorption photography

Abstract

We report the first dye laser resonance absorption photographs of a single species of aluminum ground-state neutral atoms in the plume ablated from solid aluminum by KrF excimer laser radiation. Aluminum ground-state neutral atoms were diagnosed by illuminating the ablated plume with a dye laser tuned to the 32P1/2–42S1/2 transition at 394.4 nm. Measurements have been performed in vacuum as well as in argon and air environments. Streaming velocities measured for neutral aluminum atoms in vacuum ranged from 0.5×106 cm/s at low excimer laser fluences of 1–2 J/cm2 to 3.4×106 cm/s at high fluences of 7 J/cm2. Dye laser resonance absorption photography measurements of ablated aluminum in argon and air showed slower expansion at 50 and 200 Torr, while observations at 760 Torr indicate turbulent mixing of aluminum neutrals near the surface. Differences between data in argon and air may be due to oxidation of neutral aluminum atoms.