Association Reactions of Fe⁺with Hydrocarbons: Implications for Dense Interstellar Cloud Chemistry

Reactions of Fe + with several small hydrocarbons have been studied using the selected-ion flow tube (SIFT) technique at 0.35 torr and 294 K. These reactions, which occur solely by association, are expected to have a considerable influence upon the ratio of neutral to ionized Fe-bearing species within dense interstellar clouds. Furthermore, since Fe + has generally been considered as one of the principal charge-carrying species within dense clouds, the reactions discussed here also have a very significant bearing on the overall degree of ionization within interstellar clouds. We discuss prospects for the formation of Fe-containing neutrals such as FeCO, FeC 2 H n , and FeC 4 H n ( n = 1, 2) in dissociative recombination reactions of the adduct ions expected from the reaction of Fe + with the abundant interstellar hydrocarbons C 2 H 2 and C 4 H 2 .