Dissociative photodetachment of the ethoxide anion and stability of the ethoxy radical CH3CH2O•.

The ethoxy radical is an important species in combustion chemistry; however, considerable debate regarding the fragmentation pathways exists. In order to examine the stability and dissociation dynamics of the ethoxy radical in the two lowest electronic states, dissociative photodetachment experiments at 3.20 eV were carried out on the ethoxide anion, CH3CH2O(-), and its per-deuterated isotopologue. Production of excited radicals by photodetachment of the alkoxide anion was found to lead to only CH3 + H2CO products, with no indication of the energetically allowed H-loss channel, H + CH3CHO. Ab initio calculations for the anionic and neutral surfaces, including relevant isomerization and dissociation barriers, were carried out using the CBS-QB3 method to aid in interpretation of the data. The energetics observed in the photoelectron-photofragment coincidence spectra indicate that the calculated barrier (0.70 eV) for the process CH3CH2O → CH3 + H2CO and the stability of the CH3CH2O radical relative to those products are upper limits.