Ionization and Dissociation of Hydrogen Peroxide by Electron Impact

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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.