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 Na2 dimers in the molecular beams 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 forward 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 cluster, (H2O)n, n=6,8, as reagents. This stable reactive intermediate is then able to initiate the reaction, yielding sodium hydroxdide and sodium hydride. To our surprise, our findings indicate that the 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.