Collisions of free radicals and astrophysical chemistry

Special Colloquium
Dr. Sarantos Marinakis
University of East London, UK

The past thirty years have seen an increased understanding of the role that free radicals play in astrophysical chemistry. This has been achieved by advances in spectroscopy and computational methods. The work described in this talk has focused on the role of OH, CH and PO radicals and in particular in collisions with He. The calculation of the inelastic rate coefficients of these 2pi radicals in collisions with He is a complex task because these open-shell systems are described by two adiabatic potential energy surfaces (PESs), and the radicals can populate different energy levels characterized by spin-orbit, rotational, lambda-doublet and hyperfine quantum numbers. For this reason, new ab initio PESs have been obtained, and accurate fully quantum close-coupling scattering calculations have been performed. The calculation of the inelastic rates for relevant reactions combined with existing spectroscopic work showed the role of inelastic collisions in various interstellar media (ISM). In particular, we examine their role in the ISM and in masers. Finally, the role of PO in prebiotic chemistry is also examined.