Laser‐induced breakdown spectroscopy of metals covered by water droplets

LIBS analyses of deep metallic layers were performed by dual-pulse excitation, where the first laser pulse efficiently ablates material covered by poly-dispersed water aerosol and water droplets, and the second laser pulse generates the analytical plasma on the crater's bottom. Enhancement of ablation rate in presence of water confinement was studied on various pure metals, namely Sn, Pb, Zn, Al, Cu, Fe, W, Ti and Mo. Crater depths and shapes were measured comparatively for dry surfaces and the same covered with water aerosol and water droplets of various volumes, and at different laser energies. With wet ablation using water droplet the mass removal efficiency was increased up to 20 times with respect to a dry process. The correlation between ablated mass and the thermal and mechanical properties of the examined metals was also studied.

► The deposition of water droplets on metallic samples increases the ablation rate.
► Enhancement of the ablation rate by a factor 20 × has been found for Al target.
► This result opens the possibility to analyze deep sample layers with this arrangement.
► The photothermal and mechanical effects play a significant role.