Laboratory Astrochemistry: Gas-Phase Processes

A major aim of astrochemistry is to explain the nature and abundance of the molecules observed in the interstellar medium (ISM). Three kinds of activity are involved: (a) the spectroscopic identification of the species that are present in the ISM; (b) the construction of large chemical models that attempt to explain the syntheses of the observed molecules; and (c) efforts to measure or predict crucial information, such as rate coefficients for the chemical reactions that are included in the models. Models can also be employed to identify the processes that exert a major influence on the predicted abundances of observed species. Clearly, it is important that the fundamental aspects of these processes—for example, the chemical rate coefficients—are quantified as accurately as possible. This is the role of laboratory experiments, aided by theory, and this review provides a critical examination of the experimental methods that provide these data and summarizes both the results that have been obtained for gas-phase processes and their reliability.