Reactions of H2+, HeH+, and CO 2+ ions with hydrogen atoms, and the reactions of D 2+, CO2+, CO+, N 2+ and HCN+ with deuterium atoms, were studied using ion cyclotron resonance techniques. These reactions proceed predominantly via a charge transfer mechanism. The rate constants measured are: 6.4, 9.1, 1.1, 5.0, 0.84, 0.90, 1.2, and 0.37×10-10 cm3/sec, respectively. Hydrocarbon ions of the types CHn+ and C2Hn+, where n = 2-4, do not react with H or D atoms. © 1979 American Institute of Physics.