Ion Mobility in Cooled Helium Gas (Current Topics)

Abstract

Mobilities of ions in helium gas at low temperature have been measured by using of a drift tube apparatus cooled by liquid helium. We have found that mobilities of some molecular ions are lower than the polarization limit below 100 K of the effective temperature. This finding means that the momentum-transfer cross sections become much larger than the classical ones in the ion-atom collisions of lower energies than 10 meV. The reason of this phenomenon is discussed in detail.