Non-adiabatic processes in alkali metal-alkyl halide molecule collisions: The electron harpoon

The mechanism for vibronic excitation and ion pair production in alkali metal-alkyl halide collisions is investigated. A classical trajectory surface hopping model is developed to account for the fourteen exit channels for which data is available. It is shown that the ground ionic intermediate accounts for the observed A state excitation in CH 3 I as well as the production of excited alkali atoms. It is further shown that the other, more highly excited, processes can be understood on the basis of an electron harpoon to form one of a sequence of strongly ionic doorway states. Each doorway state connecting to a manifold of exit channels. The nature of these doorway states and the role of vacancy production in their excitation is discussed.