Precision Spectroscopy of Fullerenes: Towards Resolving Astrophysical Molecular Complexity

Fullerenes --- hollow, symmetric carbon cages --- represent the largest molecules identified in astronomical environments and have dramatically altered our understanding of molecular complexity in space. Given the prevalence of the fullerenes C60, C70, and C60+ in astronomical objects, other closely related fullerenes and fullerene derivatives are also expected to be present there, but because they are challenging to study in the laboratory, accurate data required for their astronomical identification are unavailable. Employing novel laboratory techniques, this research project will yield high-resolution measurements of the long-wave infrared (LWIR) spectra of fullerenes and their derivatives that are plausible candidates for astronomical detection and may be responsible for numerous unidentified infrared emission features observed in astronomical objects such as planetary nebulae. The newly acquired spectra will be compared with data from large infrared telescopes with the goal of identifying the molecules responsible for the unidentified features. This project will directly support and train a graduate student and a postdoctoral scholar in methods of advanced laboratory astrophysics, as well as provide research opportunities to undergraduate students. Using a custom-built cavity-enhanced frequency comb spectroscopy apparatus which combines high spectral resolution, high sensitivity, and broadband detection, the research team will measure rovibrationally resolved low-temperature LWIR spectra of fullerenes and fullerene derivatives in the 6.5-10.5 micrometer wavelength region. The measurements will serve as important benchmarks for astronomical observations and quantum calculations of large molecules. Systems for study will include the symmetric fullerene C70, as well as the polar fulleranes C60H2 and C59N, whose successful measurements will pave the way for investigations of yet more complex molecules including metallofullerenes (metal-bearing fullerenes) and endofullerenes (fullerenes encapsulating an atom or a molecule). This project will take advantage of strong academic-industrial partnerships to develop novel light sources, high-resolution spectrometers, and cameras with the potential to greatly advance precision infrared spectroscopy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.