Longitudinal and Transverse Diffusion Coefficients of Mass-IdentifiedN+andN2+Ions in Nitrogen

Longitudinal and transverse diffusion coefficients for mass-identified ${\mathrm{N}}^{+}$ and ${\mathrm{N}}_2^{+}$ ions in nitrogen in an applied electric field have been measured at room temperature on the $\frac{E}{N}$ range from 12 × ${10}^{-17\mathrm{}}$ up to 300 × ${10}^{-17\mathrm{}}$ V ${\mathrm{cm}}^2$. For $\frac{E}{N}$ below about 30 × ${10}^{-17\mathrm{}}$ V ${\mathrm{cm}}^2$ the longitudinal and transverse coefficients were found to be equal and to have the value predicted by the Einstein relation. At higher $\frac{E}{N}$ both increased with increasing $\frac{E}{N}$, the longitudinal coefficient always being greater than or equal to the transverse.