Arrival Time Distributions in High‐Pressure Mass Spectrometry. II. Reactions of (H, D)3+ in Hydrogen‐Deuterium Mixtures

Arrival time distributions of ${\mathrm{H}}_3^{+}$ ions in hydrogen, ${\mathrm{D}}_3^{+}$ ions in deuterium, and of these ions and their isotopically mixed analogs in equimolar mixtures of hydrogen and deuterium have been measured using a pulsed high‐pressure ion source and individual ion flight time measurements. The ratio of the reduced mobilities of the hydronium ions in the pure gases was found to be 1.41, in good agreement with previous measurements and with the theoretical expectation of $\sqrt{2}$ . Drift velocities are linear functions of E/P but do not go through the origin because mean residence times do not accurately correspond to the reciprocal drift velocities of the ion packets. In the mixtures, however, reduced mobilities of all isotopically substituted ions are identical even though a difference by as much as 13% is expected, approximately 3 times the standard deviation. This is interpreted in terms of a rapid H⁺ or D⁺ transfer, and a lower limit of ${\text{0.9× 10}}^{\text{−10}}\hspace{0.17em}\mathrm{cc}\hspace{0.17em}{\sec }^{\text{−1}}$ is established for the rate constant of the hydron transfer reactions.