Chemical dynamics of the reaction K*(5p 2P)+H2→KH(v=0;J)+H: Electronic orbital alignment effects

Abstract

We report results from scattering state spectroscopic studies of the excited state reaction K*(5p 2P)+H2→KH(v″,J″)+H. The final state resolved action spectra allow a direct measurement of essential features of the excited state potential surfaces, including regions of local maxima and minima. We observe a pronounced blue-wing–red-wing asymmetry in the reactive to nonreactive branching ratio, peaking in the neighborhood of a strong blue wing satellite. These results show that the dominant reaction pathway passes over a small activation barrier (350±100 cm−1) in Σ+-like orbital alignment. This result is consistent with an electron jump mechanism through a K+H−H ion-pair intermediate. In contrast, approach in Π-like alignment leads predominantly to nonreactive scattering. Our results suggest that a combination of steric and energetic effects determine the major quenching pathways for alkali metal atom-H2 systems.