State-to-state reactive scattering of F+H2 in supersonic jets: Nascent rovibrational HF(v,J) distributions via direct IR laser absorption

Pulsed discharge sources of supersonically cooled F radicals have been crossed with supersonically cooled ${\mathrm{H}}_{\mathrm{2}}$ to study the $\mathrm{F}{(}^2{P}_{\text{3/2}}{,}^2{P}_{\text{1/2}}\mathrm{)+}{\mathrm{H}}_{\mathrm{2}}\to \mathrm{HF}\mathrm{(v,J)+}\mathrm{H}$ reaction under single collision conditions with a collision energy of 1.8(2) kcal/mol. The $\mathrm{HF}\mathrm{(v,J)}$ product states are probed via direct absorption of a single mode, tunable near IR laser perpendicular to the plane of intersection of the two jet axes. The high spectral resolution $\text{(Δν≈0.0001\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}})$ permits the quantum state $\mathrm{HF}\mathrm{(v,J)}$ distribution to be determined with complete resolution of final rovibrational levels. The $J$ -dependent integral cross sections for $\mathrm{HF}\text{(v=3,J)}$ are compared with exact quantum scattering calculations by Castillo and Manolopoulous on the ground adiabatic potential energy surface of Stark and Werner. Agreement between theory and experiment is quite good for low $J$ (<3) states. However, theory substantially underpredicts the experimental distributions for high $J$ (⩾3) states near the energetic cutoff for ground spin orbit state $\mathrm{F}{(}^2{P}_{\text{3/2}})$ atoms, which may indicate the presence of non-adiabatic reaction channels involving spin orbit excited ${\mathrm{F}}^{\mathrm{*}}{(}^2{P}_{\text{1/2}})$ atoms.