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 helium cooled, selected ion drift tube, at 4.35 K. Results are compared with previous experimental work at higher temperatures and, in the case of O+, comparison is made with theoretical work, where a good agreement is found. The dependence of mobility on effective temperature is discussed in light of our previous work and our measurements are related to features of the ion–atom potential. In order to facilitate further theoretical analysis, recommended values of mobility are tabulated for O+ and N+ in He and also for O+2, N+2, and CO+ in He.