Ionization of CCl4 and CCl2F2 by Electron Impact

F. B. Yousif Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Avenida Universidad #1001, Colonia Chamilpa, C. P. 62210, Cuernavaca, Morelos, Mexico Absolute partial and total cross sections for electron-impact ionization of CCl4 and CCl2F2 are reported for electron energies from threshold to 1000 eV. The product ions are mass analyzed using a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output demonstrates that all product ion species are collected with equal efficiency irrespective of their initial kinetic energies. Data are presented for production of CCl3+, CCl2+, CCl+, C+, Cl2+, and CCl32+ from CCl4; and for production of CCl2F+, CClF+, (CCl+ + CF2+), Cl+, CF+, F+, and C+ from CCl2F2. Data are also reported for formation of (CCl2+, Cl+) and (CCl+, Cl+) ion pairs from CCl4. The present partial cross sections for lighter fragment ions are found to be considerably greater than had been previously reported but the most recent total cross section measurements agree well with those reported here.