Absolute partial cross sections for electron-impact ionization of NO and NO₂ from threshold to 1000 eV

B. G. Lindsay, M. A. Mangan, H. C. Straub, and R. F. Stebbings

J. Chem. Phys. 112, 9404-9410 (2000)

Absolute partial cross sections for electron-impact ionization of nitric oxide and nitrogen dioxide are reported for electron energies from threshold to 1000 eV. The product ions are mass analyzed using a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output demonstrates that all product ions are collected irrespective of their initial kinetic energy. Data are presented for the production of NO⁺, N⁺, O⁺, and NO²⁺ ions from NO; and for the production of NO₂⁺, NO⁺, N⁺, O⁺, and (O²⁺ + N²⁺) ions from NO₂. The overall uncertainty in the absolute cross section values is ±5% for singly charged parent ions, while that for the fragment ions may be as large as ±20%. For NO, the previously published data are generally in reasonable agreement with those presented here, although there remain some significant discrepancies with even the most recent work. No previous comprehensive study of NO₂ has apparently been reported but the experimental NO₂⁺ cross section data that are available disagree substantially with the present measurements. The present total NO₂ cross section is, however, in excellent agreement with recent theoretical work.