Observation of Resonances in the F+nh3 Reaction via Transition-State Spectroscopy

Abstract

Transition state spectroscopy experiments, based on negative-ion photodechament, allow for the direct probing of the vibrational structure and metastable resonances that are characteristic of the neutral reactive surface. Here, we study the four-atom F + NH 3 → HF + NH 2 reaction using slow photoelectron velocity-map imaging spectroscopy of cryogenically cooled NH 3 F − anions. The resulting spectra reveal features associated with a manifold of vibrational Feshbach resonances in the post-transition state product well of this reactive surface. Beyond this, the spectra contain structure reporting on reactive resonances in the pre-transition state reaction complex well. Quantum dynamical calculations performed on a full-dimensional potential 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.