Absolute cross sections for electron-impact ionization of N₂O, H₂S, and CS₂ from threshold to 1000 eV

B. G. Lindsay, R. Rejoub, and R. F. Stebbings

J. Chem. Phys. 118, 5894-5900 (2003)

Absolute partial and total cross sections for electron-impact ionization of N₂O, H₂S, and CS₂ 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 ion species are collected with equal efficiency irrespective of their initial kinetic energies. Data are presented for the production of N₂O⁺, N₂⁺, NO⁺, N⁺, and O⁺ from N₂O; for production of (H₂S⁺ + HS⁺ + S⁺) and H⁺ from H₂S; and for production of CS₂⁺, S₂⁺, CS⁺, S⁺, C⁺, and CS₂²⁺ from CS₂. The total cross sections are obtained as the sum of these partial cross sections. The overall uncertainty in the absolute cross sections for most of the singly-charged ions is ±6-8%. For all three targets the cross sections for production of lighter fragment ions are found to be greater than previously reported which is consistent with the presumption of incomplete collection of energetic ions in the earlier studies. Agreement with recent theoretical calculations is satisfactory for N₂O but not for H₂S or CS₂.