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

The neutral products of irradiating a photolabile triazeno-polymer with a p ulsed laser at 248 nm (KrF excimer) were studied with time-of-flight (TOF) mass spectrometry. At fluences below 1.3 J/cm(2), N-2 is by far the most in tense neutral product. Phenyl radical (mass 76) production was also observe d. The leading edge of the N-2 TOF signal shows a shoulder corresponding to kinetic energies of about 1.1 eV, followed by a long tail that lasts hundr eds of microseconds. The tail is attributed to delayed emission of reaction products from the polymer. The kinetic energy of the fast peak is attribut ed to direct ejection of products from surface sites undergoing exothermic decomposition. The fluence dependence of the N-2 signal is highly nonlinear and is shown to fit an Arrhenius equation.