CROSS-SECTION MEASUREMENTS FOR ELECTRON-IMPACT DISSOCIATION OF CHF3 INTO NEUTRAL AND IONIC RADICALS

Absolute cross sections for electron-impact dissociation of CHF3 from the threshold to 200 eV are presented for formation of the neutral rad icals CF3, CHF2, CF2, CHF and CF. This measurement was accomplished by appearance mass spectrometry in a dual electron beam device. The thre shold energies for neutral dissociation into CF3, CHF2 and CF were mea sured to be 11.0, 13.0 and 19.5 eV, respectively. The surface loss pro bability of each radical and the electron-impact nitrogen dissociation were measured to calibrate the relative dissociation cross sections o f CHF3. The branching ratio for dissociation at 150 eV is CF3:CF2:CF:C HF2:CHF=27:5:10:2:1. In addition to the neutral dissociation, the cros s section for dissociative ionization of CHF3 was extensively measured for formation of CF3+, CHF2+, CF2+, CHF+, CF+, CH+ and F+.