On the vanishing of the t-term in the short-time expansion of the diffusion coefficient for oscillating gradients in diffusion NMR

The short-time expansion of the diffusion coefficient in powers of t^1/2 is universally connected to structural parameters of the boundaries restricting the diffusive motion. The t^1/2-term is proportional to the surface-to-volume ratio. The t-term is related to permeability and curvature. The short-time expansion can be measured by application of oscillating gradients of long total duration. For oscillating gradients, the inverse of the oscillation frequency becomes the relevant time scale. The purpose of this work is to show that the oscillating gradient approach is blind to the t-term. Thus, the t-term does not bias the determination of the t^1/2-term in experiments.