We report on the observation of a strong reorganization of the proton hydration structure in hydrated Nafion membranes following single-quantum excitation of a proton vibration with ∼4 μm light pulses. The reorganization takes place with a time constant of 170±20  fs and leads to a strong red shift of the excited proton vibration and the rise of new waterlike O–H stretch absorption bands. These observations can be explained from a vibrational-excitation-induced change of the proton-hydration structure that involves transfer of the proton charge. The results are consistent with recent quantum molecular dynamics simulations of proton transfer in Nafion membranes.

Phys. Rev. Lett.
Ultrafast Spectroscopy

Liu, L., & Bakker, H. (2014). Infrared-activated proton transfer in aqueous Nafion proton-exchange-membrane nanochannels. Phys.Rev.Lett., 112(Article number: 258301), 1–5. doi:10.1103/PhysRevLett.112.258301