Formation of a Reactive Intermediate in Molecular Beam Chemistry of Sodium and Water

The aim of this work is a theoretical study of the initial steps in the reaction of sodium and water clusters in a molecular beam. Recent experimental and theoretical works have indicated that the presence of both sodium atoms and Na<INF>2</INF> dimers in the molecular beam give rise to a chemical reaction yielding sodium hydroxide and molecular hydrogen. Furthermore, experiments seem to indicate that at least three sodium atoms are present (e.g. a dimer and a solvated neutral atom). In this study, we take a step toward answering the question of why it is necessary to have three sodium atoms present to initiate the chemistry. By means of Car−Parrinello molecular dynamics simulations we investigate the formation of the dipolar reactive intermediate using a sodium dimer and a small water clusters, (H<INF>2</INF>O)<INF>n</INF><INF></INF> (n = 6, 8), as reagents. This stable reactive intermediate is then able to initiate the reaction, yielding sodium hydroxide and a sodium hydride. To our surprise, our findings indicate that that formation of the dipolar atom is a natural state of the dimer/water cluster system; lending credibility to it being the only channel for the reactive process.