Experimental Studies Of Bimolecular Reaction Dynamics Using Pulsed Tabletop Vacuum Ultraviolet Photoionization Detection
The development and application of pulsed photoionization detection employing high intensity vacuum-ultraviolet (VUV) radiation produced by tabletop light sources has been utilized to study bimolecular reaction dynamics of phenyl radical reactions. This method employs four-wave mixing of unfocussed commercial nanosecond dye lasers in mercury vapor to generate light at 9.9 eV. Using two or three commercial pulsed nanosecond dye lasers pumped by a single 30 Hz Nd:YAG laser, generation of 0.10 mJ pulses at 125 nm (6 x 1013 photons/pulse) has been demonstrated. The VUV light source has been used as an alternative to the use of synchrotron light sources, for sensitive universal photoionization detection of products from crossed molecular beam reactions employing pulsed beam sources. In the reaction of phenyl radicals with molecular oxygen at collision energies of 64 and 97 kJ/mol, the reaction C6H5 + O2 [RIGHTWARDS ARROW] C6H5O + O was found to occur via the formation of long-lived phenylperoxy collision complexes at all collision energies. The reaction of phenyl radicals with propene has also been studied at collision energies of 84 and 108 kJ/mol. The branching ratios between methyl radical elimination, forming C8H8, and H-atom elimination, forming C9H10, were found to be 10:1 at 84 kJ/mol and 3:1 at 108 kJ/mol. By using "soft" vacuum ultraviolet photoionization at 9.9 eV for product detection, we were able to observe both product channels with negligible fragmentation. As a comparison the reaction of phenyl radicals with trans-2-butene has been studied at a collision energy of 97 kJ/mol. We only observe methyl elimination in the reaction with 2-butene and do not observe H-atom elimination.
Physical Chemistry; Molecular Reaction Dynamics; Crossed Molecular Beam Scattering
Davis, Harry Floyd
Ezra, Gregory Sion; Petersen, Poul B.
Chemistry and Chemical Biology
Ph. D., Chemistry and Chemical Biology
Doctor of Philosophy
dissertation or thesis