SYMMETRY INDUCED KINETIC ISOTOPE EFFECTS IN THE FORMATION OF AR-CENTER-DOT-CO2+

Symmetry induced kinetic isotope effects (SIKIE) have been observed ma ss spectrometrically in the termolecular association reaction of Ar an d CO?2?+ to produce Ar . CO2+ making this the first example of SIKIE i n a system where the reactants have no atoms in common. The O-18 SIKIE shows a pronounced dependence on whether the CO2+ are produced direct ly by electron ionization or indirectly by charge transfer from Ar+. T he results can be understood generally in terms of reaction restrictio ns based on a symmetry correlation scheme recently developed by one of the authors. This scheme indicates that CO2+ ions can have very diffe rent clustering reactivity with Ar depending on whether the ion is in an e (restricted) or an f (allowed) parity label state. Kinetic modeli ng of the O-18 SIKIE indicates that CO2+(e)/CO2+(f)approximate to 60 f or CO2+ produced by 21 eV electron ionization. (C) 1996 American Insti tute of Physics.