Nanosecond and Femtosecond Laser Photochemistry and Ablation Dynamics of Neat Liquid Benzenes

Abstract

Molecular mechanisms of nanosecond and femtosecond laser ablation and morphology-changing dynamics of neat liquid benzene derivatives, such as benzyl chloride and toluene, were investigated by photoacoustic measurement, nanosecond shadowgraphy, femtosecond surface light scattering imaging, and time-resolved ultraviolet−visible absorption spectroscopy. Ablation thresholds of the liquids were determined by photoacoustic measurement and shadowgraphy, whereas primary processes in ablation were elucidated by time-resolved absorption spectroscopy. Femtosecond surface light scattering imaging revealed how electronic excited/radical states evolved to nanometer morphological changes. In nanosecond laser ablation, ablation threshold value was related to photochemical reactivity producing benzyl radical; however, no correlation between the threshold and boiling point was confirmed. Indeed, a benzyl radical absorption band was clearly observed. Moreover, benzyl radical concentration at the threshold was estimated qua...