| Abstract: | The growth of molecular complexity in diffuse molecular clouds has remained a long standing problem in astrophysics. On the one hand, we have simple hydrides discovered with the \it{Herschel} space telescope and small hydrocarbon species such as \chem{C2H}, while on the other we have monolithic fullerenes including \chem{C60} and \ce{C60+}. The chemical and physical relationship between the two ends of this dichotomy remains elusive, and the species that connect the small with the large --- simple, medium-sized organic molecules possessing $>3$ carbon atoms --- have not yet been found.
Recently, we have begun a detailed observing campaign with the 100\,m Green Bank Telescope (Abstract 4275) that aims to systematically explore the growth of chemical complexity in diffuse clouds. Some of our key findings include strong absorption by \chem{C3H+}, and perhaps more excitingly, \chem{C4H}, which to our knowledge is the largest carbon chain radical detected so far in the diffuse gas. In order to fully understand the behavior of these species in what was thought to be highly hostile environments for complex chemistry, we require accurate theoretical predictions of structures and thermochemical properties pertaining to molecules that are thought to play important roles in these regions. In this talk, I will discuss our latest efforts to perform high accuracy quantum chemical calculations of several small hydrocarbon species, both as to constrain the relative energetics of their isomers, as well as high precision predictions of their spectroscopic constants to guide their searches. |
4275.pdf (21kB)