CAREER: Lifting the Veil on the Cosmochemical Cycle of Organic Matter and the Diffuse Interstellar Bands Using Ion Trap Mass Spectrometry and Cryogenic Ion Electronic Spectroscopy

For over a century astronomers have been trying to identify the source of mysterious absorption features in starlight known as Diffuse Interstellar Bands (DIBs). These features are likely caused by molecules floating in the space between stars, but their exact origin remains unknown. This project investigates whether ball-shaped molecules made entirely of carbon atoms (fullerenes) can explain these signals. Fullerenes likely form when other large molecules break apart under intense radiation in space. Using advanced laboratory instruments and spectroscopy techniques, the research team will recreate these processes under space-like conditions. They will measure the light absorption patterns of the molecules formed. Comparing these absorption signals with astronomical observations will help solve one of astronomy’s longest-standing mysteries. The project includes educational initiatives in spectroscopy and astrochemistry for graduate and undergraduate students, and science outreach activities for local schoolchildren. Building on the recent confirmation of C60+ Buckminster fullerene as the carrier of five DIBs, the proposed work investigates whether other fullerene ions, formed through photodissociation of polycyclic aromatic hydrocarbon (PAH) cations, are responsible for all DIBs. The researchers will examine how PAH cation photodissociation pathways depend on molecular size, geometry, and edge topology, focusing on the formation of stable C2n+ species (with n = 16–20). Molecular absorption lines of the resulting carbocations will be recorded using predissociation spectroscopy on cluster ions formed in a cryogenically-cooled Paul-type ion trap connected to a time-of-flight mass spectrometer. The cluster ions will be formed by tagging the cooled ions with N2. Laser radiation spanning 410–2600 nm will be used to conduct action spectroscopy. Experimental spectra will be combined with quantum chemical calculations to assign isomeric structures and characterize dissociation mechanisms. Resulting spectra will be compared against astronomical DIB observations to test the hypothesis that fullerenes formed from energetic processing of interstellar PAHs are DIB carriers. The project integrates research-driven spectroscopy instruction, computational chemistry training, development of a new undergraduate astrochemistry course, and K–12 outreach activities. 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.