A six dimensional quantum study for atom–triatom reactions: The H+H2O→H2+OH reaction

Semiclassical calculation of chemical reaction dynamics via wavepacket correlation functions

Calculation of chemical reaction dynamics is central to theoretical chemistry. The majority of calculations use either classical mechanics, which is computationally inexpensive but misses quantum effects, such as tunneling and interference, or quantum mechanics, which is computationally expensive and often conceptually opaque. An appealing middle ground is the use of semiclassical mechanics. Indeed, since the early 1970s there has been great interest in using semiclassical methods to calculate reaction probabilities. However, despite the elegance of classical S-matrix theory, numerical results on even the simplest reactive systems remained out of reach. Recently, with advances both in correlation function formulations of reactive scattering as well as in semiclassical methods, it has become possible for the first time to calculate reaction probabilities semiclassically. The correlation function methods are contrasted with recent flux-based methods, which, although providing somewhat more compact expressions for the cumulative reactive probability, are less compatible with semiclassical implementation.

OH-H2ENTRANCE CHANNEL COMPLEXES

The entrance channel to the OH+H2-->H2O+H hydrogen abstraction reaction has been investigated from several different experimental approaches and complementary theoretical calculations. Weakly bound complexes between the hydroxyl radical and molecular hydrogen have been stabilized within a shallow well in the entrance channel and characterized via electronic spectroscopy on the OH A2Sigma+-X2Pi transition. Laser-induced fluorescence and fluorescence depletion experiments have revealed the binding energy of H2/D2 with ground state OH X2Pi radicals, the intermolecular energy levels supported by the OH A2Sigma+ (v'=0,1)+H2/D2 potential, and the OH-H2/D2 excited state dissociation limit. The OH X2Pi + H2 potentials have also been examined through inelastic scattering measurements on Lambda-doublet state-selected OH with normal or para-H2. Finally, photodetachment of an electron from the H3O- anion enabled the neutral reaction to be probed in conformations sampled by the two isomeric forms of the anion.