Temperature dependence of ion mobilities: Experiment and theory

Abstract

The mobilities of several positive ions plus chloride ion in a variety of polar and nonpolar gases were measured over the temperature range 170–380 K by ICR spectrometry. The experimental results were compared to the predictions of the first-order kinetic theory for the nonpolar neutral systems. For the ion-polar neutral pairs, several theories were used for comparison. In all cases, adequate and reasonable fits were not possible. This result is attributed to theoretical shortcomings. Possible sources of error in the experimental data are discussed in detail. Other mobility measurements (mostly from drift tubes) were also compared with the kinetic theory results. The only systems which could be fit were alkali ion/rare gas neutral pairs. The mobility-temperature curves of other atomic ions and of all polyatomic ions could not be duplicated by the first-order theory.