Photodetachment of F−(H2O)n (n=1–4): Observation of charge-transfer states [F−(H2O)n+] and the transition state of F+H2O hydrogen abstraction reaction

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Abstract
We report a photoelectron spectroscopic study of F − (H 2 O) n (n=1–4) at 193 and 157 nm. In addition to a detachment feature from F − , we observed a higher binding energy feature in all spectra due to ionization of the solvent molecules leading to F − (H 2 O) n + charge-transfer states. Detachment of an electron from F − in F − (H 2 O) reaches the transition state region of the reaction, F+H 2 O→HF+OH . The bound to non-bound transition resulted in a long tail at the low binding energy side in the photoelectron spectrum of F − (H 2 O ). We estimated that the neutral F⋯H 2 O complex at the anion geometry, which is near the transition state region of the H-abstraction reaction, is 6±1 kcal/mol above the F+H 2 O asymptote, consistent with a previous estimation of a 4 kcal/mol entrance barrier height for this reaction.