KINETIC ISOTOPE EFFECTS IN GAS-PHASE MUONIUM REACTIONS

The study of the reaction dynamics of muonium (Mu), an ultralight isotope of hydrogen ((m)Mu/(m)H almost-equal-to 1/9), provides a sensitive measure of mass effects in chemical reactions. The remarkable mass difference between Mu and the other hydrogen isotopes produces large kinetic isotope effects, providing a rigorous test of calculated potential energy surfaces (PES) and reaction rate theories. The low Mu mass also necessitates careful consideration of quantum effects, i.e. tunneling in the reaction coordinate. A review of recent results in gas phase Mu chemistry is presented, including comparison with relevant H chemistry and calculated PESs, where available. The magnitude and direction of the kinetic isotope effect is shown to be a sensitive function of the PES, particularly the height and position of the saddle point.