Absolute partial cross sections for electron-impact ionization of H₂O and D₂O from threshold to 1000 eV

H. C. Straub, B. G. Lindsay, K. A. Smith, and R. F. Stebbings

J. Chem. Phys. 108, 109-116 (1998)

Absolute partial cross sections for electron-impact ionization of H₂O and D₂O are reported for electron energies from threshold to 1000 eV. Data are presented for the production of H₂O⁺+OH⁺+O⁺, O²⁺, H₂⁺, and H⁺ from H₂O and for the production of D₂O⁺, OD⁺, O⁺, O²⁺, D₂⁺, and D⁺ from D₂O. 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 completely collected. The overall uncertainty in the absolute cross section values is ±4.5% for singly charged parent ions and is slightly greater for fragment ions. The cross sections for H₂O and D₂O are found to be the same to within experimental uncertainties except for the H₂⁺ cross section which is approximately a factor of 2 greater than the D₂⁺ cross section. Previous results are compared to the present measurements.