Ion-molecule chemistry of dense interstellar clouds: Nitrogen- , Oxygen-, and Carbon-bearing molecule abundances and isotopic ratios.

We present our computer models of the ion-molecule chemistry of dense interstellar clouds modified and updated to reflect recent laboratory and theoretical information on the rate coefficients of important reactions. The emphasis in the modeling is the calculation of abundances of key observational species used to interpret cloud properties and study interstellar chemistry. Calculations were performed under a variety of density, temperature, and elemental conditions and the results compared with observations and other model calculations. Changes in the reaction network have produced several distinct differences in the work presented here compared with our (and other) earlier results, a finding which may have substantial implications for observational interpretations and program planning. In general, we find that no one set of model parameters is ideal.