Longitudinal-Diffusion Coefficient for Potassium Ions in Nitrogen at 293 K

The Bradbury-Nielsen time-of-flight technique has been used to measure the longitudinal-diffusion coefficient $D_L$ for potassium ions in nitrogen in the $\frac{E}{N}$ range $2.83<~\frac{E}{N}\left(\mathrm{Td}\right)<~28.3$, where $E$ is the electric field strength and $N$ the gas number density. The results are consistent with the value predicted by the Nernst-Townsend (or Einstein) relation to within the claimed experimental error of 3%. The variation of $D_L$ with $\frac{E}{N}$ has been compared with the predictions of Wannier, based on a Maxwellian model.