The mobility of positive ions in their own gas

Values for the mobility of positive ions of neon in neon, argon in argon, krypton in krypton and xenon in xenon have been obtained in pure gas. It is possible to deduce the mobility of an ion of the same mass as the gas atom from the known values for alkali ions in the gas on the assumption that the same mass relationship holds. In each case the observed value is considerably less, the ratio of the two being of the order of 0.60-0.75. This result may be attributed to the phenomenon of electron exchange in the case of ions in their own gas which does not arise with alkali ions. The variation of mobility with field E and pressure p has been studied. In Kr and Xe there is a marked fall of mobility with increase of E/p, at higher values the velocity of the ion increasing in a linear manner with increase of (E/p)1/2.