HYDRATED POSITIVE IONS IN NITRIC-OXIDE-WATER AFTERGLOWS

Results of measurements performed on a stationary NO-H2O afterglow are reported in this paper. The gas mixture was contained in a large, gold-plated, cylindrical chamber in which the NO was ionized by means of krypton resonance radiation. The ions from the afterglow were sampled through an electrically insulated orifice and were quantitatively detected by time-resolved mass spectrometry. For NO+ ions reacting in NO-H2O mixtures at 295 K, the product-ion mass spectrum is dominated by NO+ and its hydrates, NO+•nH2O, and by hydrated hydronium, H3O+•nH2O. The sequence of reactions leading to these products has been determined, and the rate constant for the three-body conversion of NO+ to NO+•H2O has been measured to be (1.5 ± 0.5)×10-28 cm6/sec. Bounds for several other rate constants in the reaction sequence have been obtained. The ions H3O+•2H2O, H3O+•3H2O, and H3O+•4H2O observed in the afterglow are of the same family as the hydronium ion H3O+ and its hydrates H3O+•H2O and H3O+•2H2O, which are prominent in the D region of the ionsphere. Reaction sequences similar to the one reported in this paper, which involve multiply hydrated atmospheric ions, may be an important contributors to the production of the hydrated hydronium observed in the ionosphere. © 1969 The American Physical Society.