by Kaitlynn King

Institution: Queen's University
Department: Chemistry
Year: 2015
Keywords: matrix isolation; dissociative recombination; ion chemistry; decomposition; ethane cation; fragmentation; infrared spectroscopy; charge-transfer ionization
Record ID: 2058335
Full text PDF: http://qspace.library.queensu.ca/bitstream/1974/13013/1/King_Kaitlynn_A_201504_MSC.pdf


The products of d6-ethane decomposition following charge-transfer ionization by Ar+ are studied in the present thesis to understand the reaction mechanisms that occur in the electron bombardment matrix isolation apparatus. Gas mixtures of 1:1600 d6-ethane:Ar were electron bombarded and the resulting ionization products, as well as remaining reagent molecules, were collected in a condensed matrix of argon. The products of ionization include the neutral dehydrogenation products C2D5, C2D4, C2D3, C2D2, and C2D. These products are all observed in other studies completed at the same energy of 15.8 eV, save C2D, but differ in their relative yields. Experimental parameters were explored in the present work, including relative flux of electrons, as well as relative density of electrons in the reaction zone. Using two anodes of differing geometries, the density of electrons in the reaction zone was changed, creating either a low or high ion-density environment. Altering this parameter changed the observed product distributions. C2D4 and C2D2, were the sole two products observed under low ion-density conditions, whereas all of the products listed previously were observed under the high ion-density conditions, most notably the C2D product. It is discussed that the observation of C2D, following ionization of ethane at 15.8 eV, is indicative of the occurrence of dissociative recombination processes. The other reaction processes that occur from dissociative recombination are discussed. Under low ion-density conditions, where dissociative recombination does not occur, the distribution of products is more similar to other research at an ionization energy of 15.8 eV, however differ in the relative product ratios. This is justified based on differences in reaction timescales between the present experimental work and other work on the ionization of ethane. Another experimental parameter, electron-flux, is investigated here and found to have a similar effect whether in low or high ion-density experimental conditions. The general trend is that as electron-flux increases, the extent of d6-ethane precursor consumption increases as well. Increasing the electron-flux parameter under the high ion-density conditions causes a more significant increase in reagent consumption, as compared to the same increase in the same experiment completed using low ion-density conditions.