Ultrafast Geminate Recombination Facilitated by Hydrogen-Atom Transfer in Charge Transfer Reactions from Hydroxide and Methoxide Ions

Previous transient absorption spectroscopy (TAS) hinted at an exceptionally rapid geminate recombination process in charge transfer reactions involving OH^– or OD^– ions in liquid water and CH₃O^– ions in liquid methanol. However, a comprehensive investigation of these dynamics using TAS has been hindered by the technical challenges stemming from the ultrafast spectral shift that spans a wide wavelength range from the mid-infrared to the visible on the subpicosecond time scale. To address these challenges, we have employed ultraviolet time-resolved photoelectron spectroscopy of aqueous solutions, enabling us to observe and analyze the complete dynamics, including electron detachment, solvation, and geminate recombination. Our findings are consistent with those of Iglev et al. (J. Phys. Chem. Lett. 2015, 6, 986−992), supporting the hypothesis that the structural diffusion of OH/OD/CH₃O induced by a presolvated electron plays a pivotal role in facilitating ultrafast geminate recombination.