Formation of small molecules in space through the process of radiative association

Sammanfattning: This thesis is dedicated to calculating the reaction rate constants for the formation of molecules through radiative association (RA) under interstellar conditions. The molecules that have been studied are CH, AlCl, Na+ − H2 and Al+ − H2. The CH molecule was chosen for this study because of its occurrence in several chemical reactions in the interstellar medium, the sun and comets. We decided to study AlCl because it plays a crucial role in the formation of other important interstellar compounds. The choice of studying formation of Na+ − H2 through RA is motivated by the fact that this reaction is the first and limiting step in the process of formation of NaH in the interstellar gas and is therefore of interest in astrochemistry. RA of Al+ − H2 is connected to formation of AlH in a similar manner. In order to obtain reaction rate constants, reaction cross sections had to be computed. For the diatomic molecules, the reaction cross sections were obtained using a semiclassical method and a classical method, and then compared with the cross sections calculated using quantum mechanical perturbation theory. The triatomic systems were treated using theory developed for photodissociation together with the driven equations method in the form of a driven Schr¨odinger equation.