PNNL

Abstract

Single collision reactive scattering dynamics of F + HDHF(v,J) + D have been investigated exploiting high-resolution (0.0001 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 Ecom0.6(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 [Ecom0.6(2) kcal/mol], however, the HF(v = 2,J) populations behave quite anomalously, exhibiting a nearly "flat" distribution out to J11 before dropping rapidly to zero at the energetic limit. These results provide strong experimental support for quantum transition state resonance dynamics near Ecom0.6 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 et al. [J. Chem. Phys. 112, 4536 (2000)]. These fully quantum state resolved studies therefore nicely complement the recent crossed beam studies of Dong et al. [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(2P3/2) reagent, but which are consistent with a minor (5%) nonadiabatic contribution from spin?orbit excited F*(2P1/2). ?2002 American Institute of Physics.