The infrared spectrum of protonated buckminsterfullerene C_(60)H~+

摘要

Although fullerenes have long been hypothesized to occur in interstellar environments, they have only recently been unambiguously identified through spectroscopy(1-4). C-60, C-70 and C-60(+) now constitute the largest molecular species individually identified in the interstellar medium. Fullerenes have substantial proton affinities and it has been suggested that C-60(H+) is likely the most abundant interstellar analogue of C-60 (ref.(5)). We present here a laboratory infrared (IR) spectrum of gaseous C60H+. Symmetry breaking in C60H+ produces an IR spectrum that is much richer than that of C-60. The experimental spectrum is used to benchmark theoretical spectra indicating that the B3LYP density functional with the 6-311+G(d,p) basis set accurately reproduces the spectrum. Comparison with IR emission spectra from two planetary nebulae, SMP LMC56 and SMC16, which have been associated with high C-60 abundances, indicates that C60H+ is a plausible contributor to their IR emission.