Laser ablation mechanism and plume dynamics of polyarylsulfone films studied by laser ionization time-of-flight mass spectrometry

The KrF laser ablation of polyarylsulfone (PAS) was investigated for fluenc es between 90 and 200 mJ/cm(2). Neutral fragments were probed using laser p ost ionization (193 nm) time-of-flight (TOF) mass spectrometry. Decompositi on of PAS was found to occur mainly through scission of C-S and C-O bonds a s well as via decomposition of the phenylene rings in the chain. The depend encies of both the flight velocities and the Knudsen layer temperature of t he fragments on fluence suggest that PAS ablation is;a photothermal process . In contrast, the high average translational energies (up to a few tens of eV) indicate the existence of a non-thermal component in the process. In t erms of the plume dynamics, the fitting of the arrival profiles of the frag ments with a shifted Maxwell-Boltzmann distribution over the full fluence r ange indicates the existence of a collision during the adiabatic expansion process.