Infrared spectroscopy of fullerene C60/anthracene adducts

TL;DR

This study investigates the infrared spectral signatures of C60 fullerene and anthracene adducts, suggesting they could explain some unidentified infrared features observed in space environments rich in fullerenes.

Contribution

It provides laboratory spectra of C60-anthracene adducts, demonstrating their spectral similarity to astrophysical infrared features, thus proposing a new potential contributor to space emission signals.

Findings

C60/anthracene adducts show spectral features similar to astrophysical IR emissions.

Fullerene-adducts could contribute to IR features in space environments.

Laboratory spectra support the hypothesis of adduct formation in space.

Abstract

Recent Spitzer Space Telescope observations of several astrophysical environments such as Planetary Nebulae, Reflection Nebulae, and R Coronae Borealis stars show the simultaneous presence of mid-infrared features attributed to neutral fullerene molecules (i.e., C60) and polycyclic aromatic hydrocarbons (PAHs). If C60 fullerenes and PAHs coexist in fullerene-rich space environments, then C60 may easily form adducts with a number of different PAH molecules; at least with catacondensed PAHs. Here we present the laboratory infrared spectra (~2-25 um) of C60 fullerene and anthracene Dies-Alder mono- and bis-adducts as produced by sonochemical synthesis. We find that C60/anthracene Diels-Alder adducts display spectral features strikingly similar to those from C60 (and C70) fullerenes and other unidentified infrared emission features. Thus, fullerene-adducts - if formed under astrophysical conditions and stable/abundant enough - may contribute to the infrared emission features observed in fullerene-containing circumstellar/interstellar environments.