Figure 5: Polaron modelling of proton jump times.

(a) Time τ between two proton jumps obtained from QENS on hydrated BCY20, together with three least square fits of the data points to equation (7). Solid black line represents the Ce–O stretching mode of 355 cm⁻¹. Grey dotted and solid lines are O–H stretching mode of 3,560 cm⁻¹ (ref. 15) (b) Proton jump times obtained from EIS at various pressures using equation (7). Solid red line is the fit using equation (4) and the Ce–O stretching mode (355 cm⁻¹) for the filled red squares measured at ambient pressure. The solid red line is the fit using equation (7) and the Ce–O stretching mode (355 cm⁻¹) for the proton jump time derived from EIS data at ambient pressure. The fit works well for T>500 K and deviates from low temperature data. No proper fitting to the EIS data can be obtained using the O–H stretching mode (3,650 cm⁻¹).