Tunneling Dynamics in a Double-Well Model of an H Transfer Reaction

We study the role that tunneling can play in the reaction dynamics of H atom transfer. The small mass of the H atom offers it another, nonclassical route, from reactants to products, tunneling through an activation barrier. In this work, we carefully define the portion of a reaction rate constant that is caused by tunneling in such reactions. We do this by decomposing an initial H atom wavepacket into above and below the barrier components. We show that for a very particular decomposition, the quantum dynamics of the system can be separated into two events: tunneling and above-the-barrier product production. We show for such decomposition it is possible to determine a rate constant because of tunneling alone. Finally, we demonstrate that from a single experimental observable, the overall decay of reactant concentration, one can extract structural and dynamical information about the H atom transfer reaction.