A GLOBAL VIEW OF RADIATIVE ASSOCIATION AS A FUNCTION OF PRODUCT SIZE - INTERSTELLAR IMPLICATIONS

Radiative association processes are currently thought to play a significant if not dominant role in the gas phase chemistry of dense interstellar clouds. Current detailed gas phase models of the chemistry of dense clouds contain large numbers of molecules comprising up to about 10 atoms. Radiative association will play a more important role when such models are extended to larger molecules because this process tends to increase in rate as the reactant size increases. In this paper, a current detailed theory of radiative association rate coefficients (the so-called 'phase space' theory) is utilized to determine such rate coefficients for generic reactive systems ranging in size from fewer than 10 atoms to upwards of 100 atoms. In the calculations, 'standard' molecular properties are utilized so that a global view can be obtained. The relationship between radiative association and sticking involving PAHs or 'large molecules' is considered.