Kinetic energy dependence of association reactions. A new thermokinetic method for large systems

The reactions of bare alkali metal ions (M+5Li+, Na+, or K+) with dimethoxyethane (CH3OCH2CH2OCH3 , (DXE) are studied using guided ion beam tandem mass spectrometry. The bimolecular reaction forms an associative M1(DXE) complex that is long-lived and dissociates back to the reactants. The kinetic energy dependences of the cross sections for formation of the complexes are interpreted with several different models (including rigorous phase space theory) that assume that the complex lifetimes are limited by dissociation over a loose, orbiting transition state.