Vibrational Spectroscopy of C 60 + and C 70 + in the Mid-…

In recent years, astronomical observations, in combination with laboratory spectra and theoretical modeling, have confirmed the presence of C 60 , C 60 + and C 70 across a broad range of astrophysical objects. Despite expectations that C 70 + should also be present in space, its detection is difficult to confirm due to both the lack of laboratory gas-phase IR spectra and challenges in calculating its vibrational spectrum. This study presents gas-phase IR spectroscopy of C 70 + between 6 and 9 μ m (1100−1625 cm −1 ) under astrochemically relevant conditions. The large discrepancies between the experimental and theoretical spectra of C 70 + highlight the challenges of calculating the complex vibrational spectrum of this ion and emphasize the need for laboratory data for comparison to astronomical observations. Additionally, new spectroscopic data of C 60 + are provided, showing the mid-IR spectra of both fullerene cations are dominated by features around 7 μ m, where strong emission from planetary nebulae is observed. These results are compared with emission from SMP LMC 56 and Tc 1, providing a foundation to search for C 70 + in space.