A typical singles mass spectrum of SO2 following electron ionisation at 200 eV. Note the changes in the vertical axis at m/z = 25 and m/z = 10 and the presence of signals due to the 34S isotope for the sulfur containing ions. Note also the small peak at m/z = 18 from H2O+. As discussed in the text, the low pressure of SO2 employed in these experiments, to minimize false coincidences, results in small but non-negligible signals from the background gas in the TOFMS.
Relative PICS σ r [X m +] (■) for forming fragment ions following the electron ionisation of SO2. The error bars are representative of four standard deviations of four separate measurements and, for clarity, are only given for one data point on each graph. Corresponding relative PICS extracted from the data of Lindsay et al. 8,19 (□) and Basner et al. 6 (△) are also shown where appropriate.
Relative precursor-specific PICS for forming ion fragments via single ionisation (σ1[X m +], ■) and double ionisation (σ2[X m +], ● ◯) following electron ionisation of SO2. The error bars are of 4σ and are shown for selected representive data points.
Relative precursor-specific PICS for forming: (a) S+ (Δ) and O+ (▲) via triple ionisation (inset, the same data shown on a smaller energy scale); (b) SO2+ (●) and O2+ (◯) via double ionisation; and (c) SO2+ (▲) and O2+ (Δ) via triple ionisation following electron ionisation of SO2. The error bars are representative of four standard deviations of four separate measurements and are given for a representative data point. Figure (a) has an inset showing the low energy behaviour of σ 3[O+] and σ 3[S+] on a vertical scale which is 100 times greater than that of the main figure.
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