Transition State Spectroscopy of the F + NH3 Reaction

Transition state spectroscopy experiments based on negative ion photodetachment directly probe the vibrational structure and metastable resonances that are characteristic of the neutral reactive potential energy surface (PES). Here, we study the five-atom reaction F + NH3 → HF + NH2 using slow photoelectron velocity-map imaging spectroscopy of cryogenically cooled FNH3¯ anions. Reduced-dimensional quantum dynamical simulations performed on a global potential energy surface show excellent agreement with the experimental results, allowing for the assignment of spectral structure and demonstrating that key dynamics of this bimolecular reaction are well described by this theoretical framework. Our combined experimental-theoretical study reveals features associated with a manifold of vibrational Feshbach resonances in the product well of the F + NH3 PES. At higher energies, the spectra reveal structure attributed to resonances localized across the transition state and into the reactant complex well, which may impact the bimolecular reaction dynamics.