ION MOBILITY MEASUREMENTS FOR O+ AND N+ IN HELIUM GAS AT 4.35 K

The mobilities of O+ and N+ in He have been measured using a liquid he lium cooled, selected ion drift tube, at 4.35 K. Results are compared with previous experimental work at higher temperatures and, in the cas e of O+, comparison is made with theoretical work, where a good agreem ent is found. The dependence of mobility on effective temperature is d iscussed in light of our previous work and our measurements are relate d to features of the ion-atom potential. In order to facilitate furthe r theoretical analysis, recommended values of mobility are tabulated f or O+ and N+ in He and also for O-2(+), N-2(+), and CO+ in He. (C) 199 5 American Institute of Physics.