Analytical derivation of composite mobility peaks for multiple atmospheric ions in equilibrium : Verification of Mohnen's prediction

Abstract

The concept of composite mobility peaks of multiple ion families in the atmosphere predicted by Mohnen (1977) has been theoretically verified using a general solution and a dynamic equilibrium solution of the coupled diffusion-reaction equations of an arbitrary number of ionic species. Both the general solution and the dynamic equilibrium solution have been derived by us for the sake of experimental analysis of mobility peaks to determine the transport coefficients (mobility and diffusion coefficient) and the reaction rates of multiple ions in the atmosphere. These solutions have revealed that the dynamic equilibrium is the final stage of gas-phase ion swarm phenomena where the transport and reaction of all the ions reach the complete balance, and all the ions consisting one ion family will aggregate only one mobility peak (Mohnen's prediction). We examine the reactive transport experiments of hydrated oxonium (hydronium) ion family performed by Mohnen and his colleagues, and test the commonly known mutual reaction rates from the equilibrium concentration ratio of H30+(H20)2, H30+(H20)3, and H30+(H20)4 observed by their mass spectrometer. Also, their hydronium-ammonium ion family in the atmosphere are theoretically examined by simplified 10-ions model using real transport and reaction parameters, and we calculate that only three ionic species of NH/H20, NH/NH3H20, and NH/NH3(H20)2 remain at final stage in this model.