A detailed kinetic study for the production of secondary and ternary ions in O-2(+) (Xe+)-CH3CN systems was made by applying the SIFDT techniques. "Nonprotonated complexes" (cation radical dimers or higher aggregates) of acetonitrile were present in the mass spectra of product ions. The formation of nonprotonated dimers of acetonitrile ions is ascribed to switching reactions of the ion complexes [O2 center dot+CH3CN] and [Xe center dot+CH3CN] with acetonitrile. Mathematical procedures for the treatment of kinetic dependences, in which the rate constants of the studied reactions have been determined, are described. Energy and pressure dependences of the rate constants are presented and discussed. (c) 2004 Elsevier B.V. All rights reserved.