Presentation #340.01 in the session Laboratory Astrophysics (LAD) Division Meeting: A Universe of Carbon II.
Carbon is exclusively formed in the hot interiors of stars through the fusion reactions of three alpha particles (i.e., helium nuclei) and expelled into the interstellar medium (ISM) through stellar outflows and/or supernova explosions in the late stages of stellar evolution. As the fourth most abundant element in the universe and due to its unique property to form three different types of chemical bonds through sp1, sp2, and sp3 hybridizations, carbon can be stabilized in various multi-atomic structures with different molecular configurations (i.e., allotropes), including amorphous carbon, graphite, diamond, polycyclic aromatic hydrocarbon (PAH), fullerenes, graphene, and carbon nanotubes (CNTs). Indeed, many such allotropes of carbon have alreday been seen in the ISM, either through their fingerprint spectral features in astronomical spectra (e.g., hydrogenated amorphous carbon, nanodiamonds, PAHs, C60, C70), and/or through pre-solar grains in carbonaceous primitive meteorites (e.g., graphite, nanodiamonds).
In this talk, I will focus on the photophysics of C60 as well as graphene and CNTs. I will present (1) our quantum-chemical calculations of their electronic and vibrational transitions, (2) their infrared emission spectra resulted from stochastic excitation by single photons in the ISM, and (3) their possible contribution to the ultraviolet (UV) interstellar extinction. While graphene and CNTs have not yet been detected in the ISM, their model-calculated UV extinction and IR emission spectra will be compared with the astronomical observations and allow us to constrain the abundances of these species in the ISM. Moreover, the model emission spectra will serve as a guide for JWST search for interstellar graphene and CNTs and as a basis for JWST data analysis.