Analysis of chemical dynamics via Λ doubling: directed lobes in product molecules and transition states

Many molecular processes, such as chemical reactions, inelastic collisions, photodissociation, and surface scattering, yield selective populations of Λ-doublet states. The interpretation of such experiments has been difficult, so that little quantitative information could be extracted. Based on the results of our experiment on the photodissociation of H2O, and upon calculations presented here, this situation becomes much better. We discuss processes which yield product 2Π diatomics XY in which the Λ doublets are a manifestation of two different orientations of an unpaired pπ electron orbital. Chemical dynamics which produce such selective populations indicate a stereochemical effect: for example, the unpaired pπ orbital in the XY may point in the direction of the previous bond between XY and the transition complex, and, in an energetic breakup, would have a spatial relationship to J, the total angular momentum of XY. We describe here: (a) the directions of the orbitals at high J, (b) the effect of J, and of the particular XY studied, upon the analysis, so that J-dependent chemical dynamics can be separated from those intrinsic to the molecule, (c) the effect of rotation of the reaction complex, and (d) the close relationship to polarization experiments, both LIF and chemiluminescence. We also calculate the J-dependent degree of alignment of electron density, and its dependence upon the electronic parity.