The Computed Microwave Spectrum of the Protonated Fullerene C60H+

TL;DR

This paper predicts the microwave rotational spectrum of protonated C60 (C60H+), a molecule with a permanent dipole moment, to aid its detection in space where neutral C60 is hard to observe.

Contribution

It provides the first detailed prediction of the microwave spectrum of C60H+, facilitating future astronomical detection efforts.

Findings

C60H+ has a dipole moment of about 3.8 Debye.

Protonation reduces C60 symmetry to Cs.

The study predicts specific rotational transition frequencies for C60H+.

Abstract

The largest known molecule in space, C60 , has been detected in its neutral and cationic form through its vibrational, UV-driven fluorescence emission spectrum and its electronic absorption spectrum, respectively. The detection of several polycyclic aromatic hydrocarbon molecules through their pure rotation spectrum in cold, dense, molecular cloud cores suggests that C60 might be present in these environments as well. The low flux of UV pumping photons in molecular cloud cores and the absence of suitably bright background stars, make detection of C60 and its cation through the commonly used methods impractical. As C60 has no permanent dipole moment, its pure rotational transitions are forbidden and its presence must be inferred from the rotational transitions of C60 derivatives with permanent dipole moments. Here, we present a study of the predicted rotational spectrum of protonated C60 that has a sizeable permanent dipole moment. Protonation of C60 reduces the icosahedral symmetry to Cs and results in a dipole moment of about 3.8 Debye. The resulting C60H+ is a closed shell system