THE 248-NM EXCIMER-LASER ABLATION OF LIQUID BENZENE-DERIVATIVES - A RELATION BETWEEN ABLATION THRESHOLD AND MOLECULAR PHOTOCHEMICAL REACTIVITY

The 248 nm laser ablation of liquid benzene, chlorobenzene, toluene, b enzyl chloride, and benzyl alcohol was investigated by photoacoustic, nanosecond photographic, and time-resolved spectroscopic measurements. Ablation threshold was confirmed to be correlated to photochemical re activities of molecules, while no distinct relation between the thresh old and boiling point of liquids was observed. Emissions from dissocia ted radicals responsible for the ablation were clearly detected at flu ences highly above the threshold. On the basis of these results, it is strongly suggested that a photothermal mechanism dose not have an imp ortant role, and ablation is initiated by photochemical fragmentation.