Quantum state-resolved reactive scattering of F+CH4→HF(v,J)+CH3: Nascent HF(v,J) product state distributions

Abstract

State-to-state reactive scattering of F+CH4→HF(v,J)+CH3 is studied using crossed supersonic jets and high-resolution (Δν≈0.0001 cm−1) IR laser direct absorption techniques. Rovibrational state-resolved HF column-integrated absorption profiles are obtained under single collision conditions and converted to populations via appropriate density-to-flux transformation. Nascent rovibrational distributions in each HF(v,J) state are reported. Summed over all product rotational levels, the nascent vibrational quantum state populations for HF(v) [(v=3) 0.106(3); (v=2) 0.667(14); (v=1) 0.189(27); (v=0) 0.038(78); 2σ error bars] are in agreement with previous flow cell studies by Setser, Heydtmann, and co-workers [Chem. Phys. 94, 109 (1985)]. At the rotational state level, however, the current studies indicate nascent distributions for HF(v,J) that are significantly hotter than previously reported, ostensibly due to reduced collisional relaxation effects under supersonic jet conditions. Final HF rotational states from F+CH4 are observed near the maximum energetically accessible J values in both the v=2 and v=3 vibrational manifolds, which provides experimental support for a bent F–H–C transition state structure.