Electron Affinities of O2, O3, NO, NO2, NO3 by Endothermic Charge Transfer

Abstract

Lower limits to the electron affinities of the molecules O2, O3, NO, and NO2 have been measured by determining the thresholds for endothermic charge transfer from I− to the corresponding molecules. The technique involves formation of I− by photoion-pair formation and measurement of the intensity of the product ion as a function of the energy available in the collision. The lower limits obtained are O2, 0.48 eV; O3, 1.96 eV; NO, 0.09 eV; and NO2, 2.04 eV. The threshold for the reaction I−+HNO3→NO3 −+HI has also been measured, and provides a lower limit to Δ H f0○(NO3 −). When combined with the best current estimate of ΔH f0○(NO3), it yields E.A. (NO3)≥2.48 eV.