Electron Impact Ionization Cross Sections of SiF sub 2.

Absolute cross sections are measured for electron impact ionization and dissociative ionization of SiF sub 2 from threshold to 200 eV. A fast (3 keV) neutral beam of SiF sub 2 is formed by charge transfer neutralization of SiF sub 2 sup + with Xe; it is primarily in the ground electronic state with about 10% in the metastable first excited electronic state ( a back 60 up 60 fat wig sup 3 B sub 1). The absolute cross section for ionization of the ground state by 70 eV electrons to the parent SiF sub 2 sup + is 1.38 +- 0.18 angstrom sup 2. Formation of SiF sup + is the major process with a cross section at 70 eV of 2.32 +- 0.30angstrom sup 2. The cross section at 70 eV for formation of the Si sup + fragment ion is 0.48 +- 0.08angstrom sup 2. Ion pair production contributes a significant fraction of the positively charged fragment ions.