Molecular electron affinities from collisional ionization of cesium. I. NO, NO2, and N2O

Abstract

The relative cross sections for the production of parent negative ions and O⁻ fragment ions resulting from collisions of fast cesium atoms with Maxwellian target gases of NO, NO₂, and N₂O have been studied as a function of the incident cesium beam energy from 0 to ≈40 eV. A charge exchange source is used to produce the atomic cesium beam, and the energy distribution of the cesium beam is determined by a time‐of‐flight analysis. A time‐of‐flight mass spectrometer employing ion counting techniques is used to identify the masses of the ions. Measurements of the thresholds for the charge exchange reactions yield accurate lower limits to the electron affinities of NO, NO₂, and N₂O of 0.1 ± 0.1, 2.5 ± 0.1, and − 0.15 ± 0.1 eV, respectively. The tailing of the cross section at threshold due to Doppler motion of the target gas is accounted for by a mathematical unfolding procedure.