Figure 4.

Reduced spectral density mapping of NH mobilities in PAFC (298 K). The limiting continuous curve represents the absence of internal motion, as calculated by τ_c = 3.14 ns global correlation time. Spectral densities (the strength of fluctuating radiofrequency fields from molecular rotational diffusion) at ¹⁵N frequency shown as a function of such fields close to zero frequency (slow-motion regime) [40]. JomN on the vertical axis shows the spectral densities at ¹⁵N frequency, while J0 on the horizontal axis is proportional to spectral densities close to zero frequency. The units of the two axes should be understood as 10⁻⁹ (s rad⁻¹).