Laser ablation at solid–liquid interfaces: An approach from optical emission spectra

The emission spectra from the solid–liquid interface irradiated by a pulsed laser were studied. The solid target used in this study was graphite and boron nitride, and the liquid in which the target was immersed was water, benzene, n-hexane, and carbon tetrachloride. The results showed strong continuous spectrum immediately after a pulse shot, whereas after ≈100 ns later from the irradiation it was greatly reduced, and instead, the emission from small molecules dominated the spectra. The line spectra of small molecules observed in the later time range indicate the chemical reaction between the ablated species and the species originated from the liquid molecules. The intensity of the continuous spectrum was very prominent compared to what has been observed for solid–gas interfaces. This is due to rapid electron ion recombination or bremsstrahlung due to highly confined interface plasma.