Flowing afterglow studies of hydronium ion clustering including diffusion effects

Abstract

The termolecular hydration sequence of H₃O⁺ in helium buffer gas H₃O⁺(H₂O)_n−1+H₂O+He$\underset{k_n}{\overset{k_{\mathrm{-n}}}{\rightleftarrows }}$ H₃O⁺(H₂O)_n+He is studied using the flowing afterglow technique. The rate constants k₁, k₂, k₃, and k₋₃ and the equilibrium constants K₃ and K₄ are measured, discussed, and compared with other values. The effects of mass discrimination, ion–electron dissociative recombination, and differing diffusion rates of the ions are considered, and the diffusion coefficients of the ions H₃O⁺(H₂O)_n, n=0 to 4, are estimated.