Attachment, detachment and ion-molecule reactions in SO2and SO2-O2mixtures

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Abstract
A pulsed drift tube has been employed for measurement of the electron attachment coefficient, alphaain pure sulphur dioxide over the E/N range 3.03a/(SO2) has been observed for E/N40 Td the results indicate a dissociative attachment process. Measurements of the mobility of the negative ions formed indicate the presence of at least four ions with reduced mobilities of 0.69, 0.62, 0.55 and 0.39 cm2V-1s-1respectively. Using a drift tube mass spectrometer system the ion spectra produced in pure SO2and in SO2-O2mixtures have been studied. In pure SO2at pressures around 1 Torr a number of large cluster ions are observed. At much lower pressures the predominant ion is SO2-which rapidly clusters to form SO2.SO2-as the pressure increases. When SO2is added to oxygen the following reactions are observed: O-+SO2to SO3+e; O2-+SO2to SO2-+O2. The rate for the first reaction has been measured over a range of E/N and has been found to vary between 2.0*10-9cm3s-1and 8*10-10cm3s-1. The second reaction has a rate of 3.9*10-9cm3s-1at E/N=117.2 Td.