Rate of the radiative association reaction between CH3(+) and NH3 and its implications for interstellar chemistry

A theory of radiative association reaction rates for systems in which one or more competitive exothermic binary channels exist has been developed. The theory is utilized to calculate the rate of the radiative association reaction between CH3(+) and NH3, which is important in the synthesis of CH3NH2 in dense interstellar clouds. This reaction is calculated to have a large rate coefficient despite the existence of two competitive exothermic channels. The cause of the large radiative association rate coefficient is an activation energy barrier of 2.3 eV in the dominant binary exit channel. It is suggested that a variety of other radiative association reactions, of importance to interstellar chemistry, can also occur with large rate coefficients at low temperature despite the presence of competitive exothermic channels if similar activation energy barriers are present. 18 references