EVIDENCE OF EXISTENCE OF AN HE3+ION

An ion-mobility apparatus was used to study the chemistry of helium ions in helium at gas pressures of 1-30 torr and temperatures of 300°-76°K. At temperatures below 200°K, the He2+ ion was observed to convert to an ion believed to be He3+. Identification of the He3+ was based upon observations of its behavior under varied experimental conditions. At 76°K, the rate of formation of He 3+ from He2+ was faster than the three-body formation of He2+ from He+. The rate coefficient of the latter reaction was found to be 1.7±0.4×10 -31 cm6/sec at 76°K. Between the temperatures of 135° and 200°K, He2+ and He3 + were present in equilibrium. A He3+ dissociation energy of 0.17±0.03 eV was determined from measurements of the equilibrium constant as a function of temperature.