The study of bimolecular radical reactions using a novel time-resolved photoionization time-of-flight mass spectrometry and laser absorption spectrometry apparatus

Abstract

This thesis discusses my work to design, build, troubleshoot, and utilize a novel experimental apparatus that is capable of quantitatively measuring the concentrations of reacting gas-phase species and their reactive intermediates with sufficient time-resolution and sensitivity to determine both the kinetics and the product distributions of these systems. The apparatus uses laser absorption spectrometry to probe a radical of interest and thus measure its transient concentration quasi-continuously to precisely determine the kinetics of the reaction. At the same time, the apparatus samples the reactive mixture at various reaction times after the start of reaction to determine the time-resolved product distribution of the chemical system. This combination of techniques was used to study the reactions of vinyl radicals with alkenes, which are important reactions in incipient soot formation in combustion systems. Revised chemical kinetic rate coefficients and, for the first time, temperature- and pressure-dependent product branching fractions were experimentally measured for these reactions. In addition, a new potential energy surface for the vinyl + ethene reaction was calculated using state-of-the-art F12 quantum chemistry calculations, and the master equation for this reactive system was solved using various methods to determine the temperature- and pressure-dependent rate coefficients and product branching fractions.