Mobilities and Longitudinal Diffusion Coefficients of Mass-Identified Potassium Ions and Positive and Negative Oxygen Ions in Oxygen

Abstract

Measurements at room temperature of the mobility and longitudinal diffusion coefficient have been made for low-energy mass-identified potassium ions and positive and negative oxygen ions in oxygen gas in a drift-tube mass spectrometer. The zero-field reduced mobilities of ${\mathrm{K}}^{+}$, ${\mathrm{O}}_{2}^{+}$, and ${\mathrm{O}}_{4}^{+}$ in ${\mathrm{O}}_{2}$ were found to be 2.68 \ifmmode\pm\else\textpm\fi{} 0.07, 2.24 \ifmmode\pm\else\textpm\fi{} 0.07, and 2.16 \ifmmode\pm\else\textpm\fi{} 0.08 ${\mathrm{cm}}^{2}$/V sec, respectively. ${\mathrm{O}}^{\ensuremath{-}}$, ${\mathrm{O}}_{2}^{\ensuremath{-}}$, ${\mathrm{O}}_{3}^{\ensuremath{-}}$, and ${\mathrm{O}}_{4}^{\ensuremath{-}}$ were determined to have zero-field reduced mobilities of 3.20 \ifmmode\pm\else\textpm\fi{} 0.09, 2.16 \ifmmode\pm\else\textpm\fi{} 0.07, 2.55 \ifmmode\pm\else\textpm\fi{} 0.08, and 2.14 \ifmmode\pm\else\textpm\fi{} 0.08 ${\mathrm{cm}}^{2}$/V sec, respectively. The longitudinal diffusion coefficients were measured for ${\mathrm{O}}_{2}^{+}$, ${\mathrm{K}}^{+}$, ${\mathrm{O}}^{\ensuremath{-}}$, and ${\mathrm{O}}_{2}^{\ensuremath{-}}$ in ${\mathrm{O}}_{2}$. The longitudinal diffusion coefficients of all investigated ionic species at low $\frac{E}{N}$ were at least within 16% of the values predicted from the mobilities by the Einstein relation. At higher $\frac{E}{N}$, the coefficients increased, in some cases quite rapidly, as $\frac{E}{N}$ was increased.