The vibrational spectrum of the hydrated proton: Comparison of experiment, simulation, and normal mode analysis

Abstract

The vibrational properties of the hydrated proton and deuteron in bulk phase water and deuterated water are investigated spectroscopically and computationally. Mid-infrared spectra of aqueous acid solutions are measured by attenuated total reflectance-Fourier transform IR spectroscopy and compared with pure water and salt/counterion spectra to extract high-quality hydrated proton spectra at a series of concentrations. Multistate empirical valence bond simulations of the excess proton in bulk phase water are also performed, allowing the autocorrelation function of the time derivative of the dipole moment, and hence the power spectrum of the hydrated proton, to be evaluated. The experimental and theoretical spectra are found to be in very good agreement. Normal mode analysis of the bulk phase simulation data allows definitive assignment of the spectrum. The associated motions are found to be represented by both Eigen and Zundel forms of the hydrated proton.

Interfacial Structures of Acidic and Basic Aqueous Solutions

“…In recent years, there has been a great deal of discussion on the existence of hydronium ions and their OH stretch frequencies. Infrared spectroscopic studies on clusters (n = 5) 27 and bulk HCl solutions 28 suggest the presence of hydronium ions with a stretch frequency around ~2900 cm -1 . Raman studies found a very broad band (called proton continuum) below ~3200 cm -1 which was attributed to H 3 O + ad H 5 O 2 + .…”

Dynamical aspects of intermolecular proton transfer in liquid water and low-density amorphous ices

“…7 the physical origin of the bands observed in S p (ω). We have chosen to show the full frequency range, although the spectral domain where proton vibrations are located is between 1500 and 3600 wave numbers [69].…”

“…Infrared spectra are measured through the absorption coefficient, α(ω) or, equivalently, by means of the imaginary part of the dielectric constant, ε (ω) [68]. Such quantum properties can be computed in the EVB framework with the aid of an absorption lineshape function I (ω), i.e., the Fourier transform of the time derivative of the dipole momentμ(t) [42,69]. In the present study, we have used another observable, the velocity autocorrelation function of the lone proton…”

Transport in Proton Conductors for Fuel‐Cell Applications: Simulations, Elementary Reactions, and Phenomenology

“…Simultaneously, Borgis and Vuilleuimier [83][84][85][86][87] and Voth and co-workers [88][89][90][91][92][93] developed multistate EVB models for proton transport in aqueous solution. In their models, a protonated cluster involving n water molecules, H 2n+1 O n + , is described by n zeroth-order VB states.…”