Proton Tunneling: A Decay Channel of the O-H Stretch Mode inKTaO3

Abstract

The vibrational lifetimes of the O-H and O-D stretch modes in the perovskite oxide KTaO3 are measured by pump-probe infrared spectroscopy. Both stretch modes are exceptionally long lived and exhibit a large "reverse" isotope effect, due to a phonon-assisted proton-tunneling process, which involves the O-Ta-O bending motion. The excited-state tunneling rate is found to be 7 orders of magnitude larger than from the ground state in the proton conducting oxide, BaCeO3 [Phys. Rev. B 60, R3713 (1999)].

Ultrafast Proton/Deuteron Dynamics in Solid Oxide Observed with Infrared Pump-Probe Spectroscopy

“…This long lifetime compared with other vibrational modes in condensed phases indicates that OD mode is isolated from the phonon bands which cause the energy relaxation. We note that, although the bleaching signal of OH/OD modes in the same material has been observed [4], this is the first observation of the 1-2 transition in solid oxide by IR pump-probe measurement. The 1-2 transition frequency is found to be redshifted by 92 cm -1 , so that the potential anharmonicity is determined to be 3.6 %.…”

Kinetic Isotope Effects Provide Experimental Evidence for Proton Tunneling in Methylammonium Lead Triiodide Perovskites

“…The authors propose that this barrier would be further reduced if nuclear quantum effects such as tunneling are taken into consideration. Indeed, the quantum effect on proton conduction is a usual occurrence in the case of perovskite oxides, or metals . In light of the theoretical simulations reported by Egger et al, which considered deprotonation of the MA ion as a possible source of migrating hydrogen, it is reasonable to assume that proton migration is coupled to the MA ion rotation .…”

Structure–property correlation in oxide-ion and proton conductors for clean energy applications: recent experimental and computational advancements

“…Studies of ion conduction under the condition of mode-selective vibrational excitation may provide new insight into this matter. 120,121,123,124 Another interesting trend in recent work relates to the application of a modied version of the Chudley-Elliott jump diffusion model to account for coherent scattering in QENS studies of solid oxide-ion conductors. In the future, this approach may be extended to systems featuring mixed coherent-incoherent scatterers, such as mixed proton-oxide-ion conducting systems.…”