Emission of neutral molecules during UV laser ablation of a photolabile triazeno polymer

Abstract.

The neutral products of irradiating a photolabile triazeno-polymer with a pulsed laser at 248 nm (KrF excimer) were studied with time-of-flight (TOF) mass spectrometry. At fluences below 1.3 J/cm², N₂ is by far the most intense neutral product. Phenyl radical (mass 76) production was also observed. The leading edge of the N₂ TOF signal shows a shoulder corresponding to kinetic energies of about 1.1 eV, followed by a long tail that lasts hundreds of microseconds. The tail is attributed to delayed emission of reaction products from the polymer. The kinetic energy of the fast peak is attributed to direct ejection of products from surface sites undergoing exothermic decomposition. The fluence dependence of the N₂ signal is highly nonlinear and is shown to fit an Arrhenius equation.