Spectroscopic observation of resonances in the F + H₂ reaction

Photodetachment spectroscopy of the FH₂^- and FD₂^- anions allows for the direct observation of reactive resonances in the benchmark reaction F + H₂ → HF + H. Using cooled anion precursors and a high-resolution electron spectrometer, we observe several narrow peaks not seen in previous experiments. Theoretical calculations, based on a highly accurate F + H₂ potential energy surface, convincingly assign these peaks to resonances associated with quasibound states in the HF + H and DF + D product arrangements and with a quasibound state in the transition state region of the F + H₂ reaction.The calculations also reveal quasibound states in the reactant arrangement, which have yet to be resolved experimentally.