Infrared spectroscopy of ionized fullerene derivatives: The astrophysical implications of breaking symmetries
Dr. Julianna Palotas
University of Maryland
Despite its conceived emptiness, interstellar space is full of atoms, molecules and particles in large variety. On the one hand, observation of these species can serve as a sensitive probe for the physical conditions in inter- and circumstellar environments. On the other hand, understanding astrochemistry itself can reveal the chemical evolution in space, including the chemical processes in the formation of planetary systems, prebiotic evolution and eventually the chemical origin of life. In this ambitious exploration, astronomical observations, theoretical modelling and laboratory experiments are equally important and are closely intertwined.
In this presentation, the focus is on the laboratory aspects of astrochemistry, and in particular on the infrared fingerprints of large carbonaceous molecular ions: fullerenes and polyaromatics. Fullerenes, C60 and C70, constitute the largest molecular species individually identified in the interstellar medium. Not only the neutral molecules, but also other fullerene related compounds have been proposed to be present in outer space. Besides the obvious fullerene ions, these species include ionized exohedral complexes formed from C60 and abundant elements (Na, K, H, O, etc). Compared to the icosahedral C60 that has a very sparse spectrum, ionization and/or functionalization of the bare fullerene breaks its high symmetry and results in a very rich spectrum.
We present here the first laboratory infrared spectrum of gaseous C60H+, C70H+ and oxidized C60. Combined analysis of the experimental spectra and spectra computed at the density functional theory level enables us to evaluate the protonated isomers being formed.Comparison with IR emission spectra from planetary nebulae that have been associated with high fullerene abundances indicate that various ionized fullerene derivatives are plausible contributors to their IR emission.