Quantum calculations of the photoelectron spectra of the OH-•NH3 anion: implications for OH + NH3 → H2O + NH2 reaction dynamics

We present the results of quantum dynamics calculations for analyzing the experimentally measured photoelectron spectra of the OH-center dot NH3 anion complex. Detachment of an excess electron of OH-center dot NH3 initially produces a molecular arrangement, which is close to the transition-state structure of the neutral OH + NH3 -> H2O + NH2 hydrogen abstraction reaction due to the Franck-Condon principle, and thus finally leads to the OH + NH3 or H2O + NH2 asymptotic channel. We used both the path integral method and the reduced-dimensionality quantum wave packet method to simulate the photoelectron spectra of the OH-center dot NH3 anion. The calculated spectra were found to be in qualitative agreement with the experimental spectra. It was found that the photodetached complex mainly dissociates into the OH + NH3 channel; however, we found that the hydrogen exchange process also contributes to the photodetachment spectra.