Mass spectrometric determination of partial electron impact ionization cross sections of No, No2, and N2O from threshold up to 180 eV

Electron impact ionization of nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O) has been studied as a function of electron energy up to 180 eV with a double focussing mass spectrometer Varian MAT CH5 and an improved Nier type electron impact ion source. Relative partial ionization cross sections were measured for the processes NO+ + 2e, NO++ + 3e, and NO2 + e -> NO+2 + 2e, NO++ + 3e and N2O + e -> N2O+ + 2e. An accurate measurement of the cross section ratios q(NO2+/NO)/q(NO+/NO) and q(NO22/NO2)/q(NO+2/NO2) has been made. Relative cross section functions were calibrated absolutely with two different normalization methods. Moreover, both metastable and collision induced dissociations of N2O+ were studied quantitatively using the technique of decoupling the acceleration and deflection electric fields. Using the n- th root extrapolation the following ionization potentials have been derived from the cross section functions near threshold: NO+(X1Σ+); NO++; NO+2; NO2++; N2O+(X2π). These results are compared with previous measurements and theoretical calculations, where available. Part of the results presented have been already published in seven papers by the author. (Author)