Infrared spectra of protonated and deuteronated C 60 in interstellar environments

Abstract

With the credible detection of C60, C70 and C70+ in the interstellar medium (ISM), new prospects have opened up for the search of other fullerenes and their derivatives. Since fullerenes show high proton affinities, their protonated forms should predominate in the ISM, which can easily go through deuterium enrichment. Here, we present the infrared (IR) spectra and standard enthalpy of formation of C60H+, C60D+, C60H18+ and C60D18+ using Density Functional Theory (DFT) in singly ionized forms. The obtained computed IR spectra are compared with the observations. The results show that the four mid-infrared bands of neutral C60 are still visible in C60H+ and C60D+, but their strength diminishes in C60H18+ and C60D18+. As a conclusion, it is possible that the IR bands ascribed to C60 are a mixture of pure and slightly protonated and deuteronated fullerenes. In this way, the observed scattering of the C60 band ratios could be explained. © 2023, Indian Academy of Sciences.