PARTIAL CROSS-SECTIONS FOR ELECTRON-IMPACT DISSOCIATION OF CF-4 INTO NEUTRAL RADICALS

The electron energy dependence of partial cross sections for dissociation of carbon tetrafluoride (CF4) into neutral radicals CF3, CF2 and CF has been measured. This was accomplished with threshold-ionization mass spectrometry in a differentially pumped dual-electron-beam device. The threshold energy for dissociation into each neutral radical was measured for the first time to be 12.5 eV, 15.0 eV and 20.0 eV for CF3, CF2 and CF radicals, respectively. The absolute cross sections for electron impact energy between 10 and 300 eV were determined through measurements of the radical sticking coefficient and electron-impact nitrogen dissociation. The magnitude of the cross section at its maximum is 0.39 x 10(-20) m2 at 120 eV for CF3 radical, 0.22 x 10(-20) m2 at 130 eV for CF2 radical, and 0.21 x 10(-20) m2 at 110 eV for CF