The formation of molecules in diffuse interstellar clouds

Abstract

A chemical system involving carbon and hydrogen is used to obtain steady-state abundances of a number of molecules over a wide range of densities. The calculated CH abundance agrees well with the astronomical observations. For reasonable values of the rate coefficients, the present system of reactions cannot explain, simultaneously, the measured abundances of CH and CH(+). An abundance of C2H comparable to the abundance of CH is predicted for diffuse clouds.