Spectroscopic observation of resonances in the F + H2 reaction

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Science  31 Jul 2015:
Vol. 349, Issue 6247, pp. 510-513
DOI: 10.1126/science.aac6939

Glimpsing resonances as F and H2 react

The reaction of fluorine atoms with hydrogen molecules has long provided a window into the subtle effects of quantum mechanics on chemical dynamics. Kim et al. now show that the system still has some secrets left to reveal. The authors applied photodetachment to FH2 anions and their deuterated analogs. This allowed them to intercept the reaction trajectory in the middle and thereby uncover unanticipated weakly bound resonances. Theoretical calculations explain these observations and predict additional similar features that have yet to be seen.

Science, this issue p. 510


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.

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