Free Radical-Surface Interactions Using Multiphoton Ionization of Free Radicals

摘要

Free Radical and Atom Surface interactions have been studied in a low pressure reactor (Knudsen cell) where the atomic and molecular transients predominantly collide with the walls of the reaction vessel. The approach taken involved generating the neutral transients using IR-multiphoton decomposition of an appropriate precursor and subsequently exposing the photolysis products to given surfaces at variable temperature (ambient to 450 C). The detection was performed by molecular beam sampling mass spectrometry and in situ Resonance enhanced Multiphoton Ionization using a tunable dye laser. The combination of both techniques affords the possibility to determine the kinetics of the neutral transients in quantitative terms, that is competition between first order and second-order processes, and the determination of quantitative REMPI ionization cross sections. The heterogeneous loss rate constants are cast in the form of a sticking coefficient for a specific radical on a given surface. We have investigated the interaction of CF3 radical on SiO2 and Si over a range of temperatures. SiH2 has been investigated in its interaction with solid Si- containing surfaces, and I and Br atoms have been studied as to their reaction with various surfaces. Sticking coefficients, Free radicals atoms, Cross section, Silicon, Carbon trifluoride, Silicon dioxide. (mjm)