Transverse diffusion of Ar+ and Ar2+ in Ar at 298K

A new approach to measure values of the transverse diffusion coefficient from a drift tube experiment is presented. The analysis of the E/N dependence (E is the electric field strength and N is the neutral gas density) of the count rate of ions transversing a drift tube from a point source to a point exit aperture enables a determination of the variation of DT/K (DT is the transverse diffusion coefficient and K is the ionic mobility) with E/N for singly and doubly charged atomic Ar ions in Ar at 298K. Absolute values of DT/K may be obtained by normalisation at low E/N to the Nernst-Townsend value. The two ion types measured to be 55 mV for Ar+ and 125 mV for Ar2+. This difference is believed to be related to the relative roles played by charge exchange in the drift motion of the two ion types. The analysis further discloses that the reaction rate coefficient for the loss of Ar2+ by collisions with H2O is 3*10-9 cm3 s-1.