Thermal Energy Ion—Neutral Reaction Rates. I. Some Reactions of Helium Ions

A flowing, steady-state afterglow system has been utilized to measure room-temperature ion—neutral reaction rates. A description of the apparatus and technique is given. Measured rate constants for He+ reactions with O2, N2, CO, NO, and CO2 are reported, as well as upper limits for the reactions of He+ with H2, Ne, and Ar, and an estimate for the reaction of He2+ with Ne and N2. The reactions of He+ with O2, N2, CO, NO, and CO2 are all rapid, the rate constants all being ≈10−9 cm3 sec−1, implying essentially a reaction per collision.