Analysis of solids by laser ablation and resonance-enhanced laser-induced plasma spectroscopy

An analytical technique based on resonance-enhanced laser-induced plasma spectroscopy was demonstrated. Pellets of potassium iodate containing trace amounts of sodium were ablated by a 532-nm laser pulse in air. After 30 ns, the plasma plume was intercepted by a 404.4-nm laser pulse to resonantly photoionize the potassium atoms in the vapor plume. The 589-nm emissions of the sodium were found to be significantly enhanced. The enhancement was shown to depend critically on the profile of the 532-nm beam as well as the spatial overlap of the two laser pulses. Using this double-pulse scheme, the mass detection limit for sodium was estimated to be about 200 pg, which was five times better than that obtained by using the 532-nm laser pulse alone.