title: Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy.
abstract: We employed ultrafast transient absorption and broadband 2DIR spectroscopy to study the vibrational dynamics of aqueous hydroxide solutions by exciting the O-H stretch vibrations of the strongly hydrogen-bonded hydroxide solvation shell water and probing the continuum absorption of the solvated ion between 1500 and 3800 cm(-1). We observe rapid vibrational relaxation processes on 150-250 fs time scales across the entire probed spectral region as well as slower vibrational dynamics on 1-2 ps time scales. Furthermore, the O-H stretch excitation loses its frequency memory in 180 fs, and vibrational energy exchange between bulk-like water vibrations and hydroxide-associated water vibrations occurs in ∼200 fs. The fast dynamics in this system originate in strong nonlinear coupling between intra- and intermolecular vibrations and are explained in terms of non-adiabatic vibrational relaxation. These measurements indicate that the vibrational dynamics of the aqueous hydroxide complex are faster than the time scales reported for long-range transport of protons in aqueous hydroxide solutions.
authors.affiliation: Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Aritra
authors.initials: A
authors.lastname: Mandal
authors.affiliation: Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Andrei
authors.initials: A
authors.lastname: Tokmakoff