Probing the transition state via photoelectron and photodetachment spectroscopy of H(3)O(-).

The H(3)O(-) anion has stable and metastable structures that resemble configurations in the vicinity of the transition state for the neutral reactions OH + H(2) <--> H(2)O + H. Photoelectron spectroscopy of this anion probes the neutral reaction dynamics in the critical transition-state region. Accurate quantum dynamics calculations of the photoelectron intensity and photodissociation product energies are shown to provide a quantitatively reliable means of interpreting such experimental observations and reveal a detailed picture of the reaction dynamics.