Laboratory studies of bimolecular reactions of positive ions in interstellar clouds, in comets, and in planetary atmospheres of reducing composition

Abstract

Laboratory results are presented for over 200 bimolecular ion-molecule reactions of importance in the chemistry of interstellar clouds, comets, and planetary atmospheres with reducing compositions. The product distributions and rate constants measured for these reactions at 300 K using ion cyclotron resonance methods are given in 23 tables covering the reactions of H +, He +, Ne+, Ar+, C+, N+, S+, H2+, CH+, OH+, NH+, HS+, H8+, H2O+, NH2+, H2S+, NH3+, CH2+, CH3 +, CH4 +, C2H2 +, C2H3 +, C2H4 +, C2H5 +, C2H6 +, and several other ions with many stable neutral molecules including H2, 02, N2, CO, NO, CO2, N2O, HCN, H2O, NH3, H2S, H2CO, CH4, C2H2, C2H4, and C2H6. A special compilation is given for the reactions of the above ions with H2, which also includes the reactions of 0+, HeH+, CO+, NO+, CN+, HCN+, HCO+, H2CO +, C2 +, N2 +, 02+, C2H +, O2H +, and C2H2 + ions with H2 as well as the exchange reactions of several ions with isotopic hydrogen molecules. In addition to the experimental data, some prescriptions are given for predicting the most probable product channels for reactions for which there are no experimental data yet available. These prescriptions are based on the compilation of observed preferred product channels for reactions involving a particular ion. These laboratory data and prescriptions are used in a few cases to illustrate applications to recent work modeling the chemistry of interstellar clouds, comets, and the atmospheres of the Jovian planets and their satellites. The areas of astrophysical chemistry in which further laboratory work is required are also briefly examined. Subject headings: comets - interstellar: molecules - laboratory spectra - molecular processes - planets: abundances