Alkali¿hydrogen reactions

Highly endoergic alkali-hydrogen reactions are usually initiated by electronic excitation of the alkali atom. This implies that non-adiabatic couplings take place along the reaction path, the collision mechanism being dominated by the electron transfer jump that occurs between the alkali atom and the hydrogen molecule. Since electronic excitation can be selectively achieved over many atomic states, these reactions constitute good candidates to generalize the study of non-adiabatic processes in reaction dynamics. Series of heat-pipe oven and crossed-beam experiments have been carried out over the Li + H 2, Na + H 2, K + H 2, Rb + H 2 and Cs + H 2 reactions, in which high-resolution optical techniques have been used for reagent excitation and product characterization. The experimental findings indicate that, in spite of common characteristics, the five reactions exhibit apparently different behaviours that are not explained by usual collision models. However, a critical analysis based on the few calculation...