Picosecond Coherent Raman Study of Solid-State Chemical Reactions during LaserPolymer Ablation

摘要

Multiplex picosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS)is used to study the dynamics of a thin film of a polymer, polymethyl methacrylate (PMMA), undergoing photothermal laser ablation. Time dependent CARS spectra of a PMMA Raman transition near 810 /cm reveal line broadening, attributed to temperature increase, peak shift, attributed to rapid volume expansion, and the appearance of a new peak attributed to the formation of methyl methacrylate by picosecond time scale polymer thermal decomposition. This is believed to be the first direct observation of a chemical reaction product in the solid itself, during laser ablation. Coherent Anti-Stokes Raman Spectroscopy (CARS), Polymer, Polymethyl Mathacrylate (PMMA), Laser ablation.