Ionization of C3F8 by electron and ion impact

The dissociative ionization of perfluoropropane, C3F8, by electron impact h as been measured under single collision conditions using Fourier Transform Mass Spectrometry. The total ionization cross-section rises to a maximum va lue of 1.24 +/- 0.20 x 10(-15) cm(2) at 140 eV. CF3+ is the most prominent ion fragment at all energies, followed by C3F7+, CF+, CF2+, C2F4+ and C2F5: C3F8+ is not observed. The ratio of dissociative ionization to total diss ociation increases from 35 +/- 8% at 22 eV to no less than 70% from 70 to 2 00 eV. Among the ion fragments only C3F7+ reacts at room temperature to pro duce C2F5+. (C) 2000 Elsevier Science B.V. All rights reserved.