Mobilities and longitudinal diffusion coefficients of K+ ions in argon gas

Abstract

We have used a drift tube mass spectrometer to measure the mobilities and longitudinal diffusion coefficients of mass‐identified K+ ions in argon at 300°K. The range of E / N extended from 1 to 610 × 10 −17 V · cm 2 , where E is the electric drift field intensity and N is the number density of the neutral gas. The zero‐field reduced mobility of K+ ions in argon was found to be 2.66 ± 0.05 cm 2 / V · sec , in close agreement with the value previously reported by Tyndall for ions in argon that were assumed to be K+ but not mass identified. The low‐field diffusion coefficients agree well with the value predicted from the Einstein equation using the experimental zero‐field mobility. Our diffusion data are compared with theoretical predictions of Wannier and of Whealton and Mason, and with experimental data obtained by Skullerud using a drift tube lacking a mass spectrometer.