Ionization and Dissociation of Hydrogen Peroxide by Electron Impact

Abstract

Mass spectrometric measurements on hydrogen peroxide were carried out with a modulated molecular beam sampling system to eliminate interferences from decomposition products. The mass spectrum of pure hydrogen peroxide differs considerably from previously reported spectra, which did not include an estimate of the H₂O⁺ and O₂⁺ ion intensities because of decomposition problems. Appearance potentials of the ions were measured with the following results: I(H₂O₂) = 10.92±0.05 ev, A(HO₂⁺) = 15.36±0.05 ev, A(O₂⁺) = 15.8±0.5 ev, A(H₂O⁺) = 14.09±0.10 ev, A(OH⁺) = 15.35±0.10 ev, and A(O⁺) = 17.0±1.0 ev. The ionization processes and relevant thermochemical energies are discussed. It is found that the H₂O⁺ and OH⁺ ions are evolved without excess energy, while the dissociative processes producing O₂⁺ and O⁺ require excess energy.