Reactive scattering of F+HD→HF(v,J)+D:: HF(v,J) nascent product state distributions and evidence for quantum transition state resonances

Single collision reactive scattering dynamics of F+HD-->HF(v,J)+D have been investigated exploiting high-resolution (Deltanuapproximate to0.0001 cm-1) infrared laser absorption for quantum state resolved detection of nascent HF(v,J) product states. State resolved Doppler profiles are recorded for a series of HF rovibrational transitions and converted into state resolved fluxes via density-to-flux analysis, yielding cross-section data for relative formation of HF(v,J) at E(com)approximate to0.6(2), 1.0(3), 1.5(3), and 1.9(4) kcal/mol. State resolved HF(v,J) products at all but the lowest collision energy exhibit Boltzmann-type populations, characteristic of direct reactive scattering dynamics. At the lowest collision energy [E(com)approximate to0.6(2) kcal/mol], however, the HF(v=2,J) populations behave quite anomalously, exhibiting a nearly "flat" distribution out to Japproximate to11 before dropping rapidly to zero at the energetic limit. These results provide strong experimental support for quantum transition state resonance dynamics near E(com)approximate to0.6 kcal/mol corresponding classically to H atom chattering between the F and D atoms, and prove to be in remarkably quantitative agreement with theoretical wave packet predictions by Skodje [J. Chem. Phys. 112, 4536 (2000)]. These fully quantum state resolved studies therefore nicely complement the recent crossed beam studies of Dong [J. Chem. Phys. 113, 3633 (2000)], which confirm the presence of this resonance via angle resolved differential cross-section measurements. The observed quantum state distributions near threshold also indicate several rotational states in the HF(v=3) vibrational manifold energetically inaccessible to F(P-2(3/2)) reagent, but which are consistent with a minor (less than or similar to5%) nonadiabatic contribution from spin-orbit excited F-*(P-2(1/2)). (C) 2002 American Institute of Physics.