Temperature dependence of the mobility and association rate coefficient of He+ ions in He from 30-350 K

The temperature dependence of the mobility of He+ ions in He and of the three-body association reaction He+ + 2He→He2+ + He have been studied in a liquid-helium-cooled ion drift tube for temperatures from 30 to 350 K. The results for the mobilities agree very well with some theoretical models where the agreement depends on the interaction potential used in the calculations. The measured association rate coefficients can be approximated by the expression k = 1.4 x 10-31(300/T)sup(0.6+-0.1). The observed temperature dependence is in good agreement with several previous theoretical calculations. (author)