ABSOLUTE CROSS-SECTIONS FOR THE ELECTRON-IMPACT IONIZATION OF THE NF2 AND NF FREE-RADICALS

We report measurements of the absolute cross sections for the electron-impact ionization of the NF2 and NF free radicals from threshold to 200 eV At 70 eV, the absolute parent NF2 and NF ionization cross section are 1.25+/-0.23 angstrom2 and 1.05+/-0.19 angstrom2, respectively. We found little evidence of the presence of vibrationally excited radicals in the incident target beam for both NF2 and NF. We also studied the dissociative ionization of NF2 and NF. The absolute cross section for the formation of the NF+ fragment ions from NF2 was found to be 0.75+/-0.15 angstrom2 at 70 eV The NF+ fragment ions are formed with little excess kinetic energy. The only significant pathway leading to the observed NF+ fragment ions is the single positive ion formation. Our data show no indication of the presence of double positive ion formation channels or positive-negative ion pair formation processes. Cross sections for the formation of the atomic fragment ions F+ and N+ from both NF2 as well as NF were found to be small with maximum values of less than 0.1 angstrom2 at 70 eV in all cases.