Dissociative electron attachment studies with applications to monitoring technological plasmas

• Main Author: Gilmore, Thomas
• Published: Queen's University Belfast 2017
• Subjects: 530
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726357

This thesis presents several investigations into dissociative electron attachment to a number of different molecules. Negative ion formation of the biologically and astrophysically relevant molecule pyrimidine is studied in detail, along with the closely related molecules pyridazine, pyrazine and s-triazine. Although the diazines are electronically very similar and have the same mass, they are found to have distinctive dissociative electron attachment spectra. New absolute cross sections for dissociative electron attachment to HCCCN are also reported. The method for calculating cross sections for the azines fs applied to previously published data for HCCCN, but additionally total cross sections for electron impact ionization were calculated. This was done using the Binary-Encounter Bethe (BEB) method. The experimental method used to collect data for the molecules mentioned above can be adapted to monitor technological plasmas In real time. Previously, a portable mass spectrometer called PRISM was developed in Queen’s University Belfast, but was too large and complicated to be used in industrial environments. Using Monte Carlo simulations, a new design was found that only uses a single parabolic electrode but is sufficient to match the previous performance of PRISM. The new mass spectrometer has the advantages of perfect space focussing and that it can be scaled to any size, limited only by the resolution of the timing circuitry. R-matrix calculations are presented for low energy electron scattering to the diatomic molecules CO and CS. By examining the energies at which the resonance curves intersected each molecule’s Franck-Condon region, the resonances are correlated to dissociative electron attachment resonances observed experimentally. The R-Matrix calculations for CO and C6 compare well to experimental results, with the calculated resonant energies typically within 1 eV from experimental values.