Proton-transfer spectroscopy beyond the normal-mode scenario

Abstract

A stochastic theory is developed to predict the spectral signature of proton-transfer processes and applied to infrared spectra computed from ab initio molecular-dynamics simulations of a single H${}_5$O${}_2{}^{+}$ cation. By constraining the oxygen atoms to a fixed distance, this system serves as a tunable model for general proton-transfer processes with variable barrier height. Three spectral contributions at distinct frequencies are identified and analytically predicted: the quasi-harmonic motion around the most probable configuration, amenable to normal-mode analysis, the contribution due to transfer paths when the proton moves over the barrier and a shoulder for low frequencies stemming from the stochastic transfer-waiting-time distribution; the latter two contributions are not captured by normal-mode analysis but exclusively report on the proton-transfer kinetics. In accordance with reaction kinetic theory, the transfer-waiting-contribution frequency depends inverse exponentially on the barrier height, whereas the transfer-path-contribution frequency is rather insensitive to the barrier height.

References in corpus (5)

• Canonical sampling through velocity-rescaling
• How to remove the spurious resonances from ring polymer molecular dynamics
• Full dimensional (15D) quantum-dynamical simulation of the protonated water-dimer II: infrared spectrum and vibrational dynamics
• Time-dependent friction effects on vibrational infrared frequencies and line shapes of liquid water
• Hydrated Excess Protons in Acetonitrile/Water Mixtures - Solvation Species and Ultrafast Proton Motions

Cited by in corpus (1)

• Spectral signatures of excess-proton waiting and transfer-path dynamics in aqueous hydrochloric acid solutions