ArCH2+: A Detectable Noble Gas Molecule

The noble gas molecular cation, ArCH2+, has been observed in mass spectrometry experiments, and the present work is providing high‐level quantum chemical predictions for the vibrational and rotational spectroscopic data necessary to observe this molecule <italic>in situ</italic> in other laboratory conditions. The Ar‐C stretch in this cation is a bright fundamental vibrational frequency that should be observable in the early regions of the far‐infrared at 421.2 cm‐1 for the universally most common 36Ar isotope. The near‐prolate nature of this molecule and its 2.91 D dipole moment should also make it distinguishable for submillimeter detection, as well. Furthermore, the Ar‐C bond strength in ArCH2+ is greater than the global minimum for the dissociation of the experimentally known ArOH+ cation. As a result, the infrared spectrum of this simple organo‐noble gas molecule is likely waiting to be observed and may already exist in the spectra of hydrocarbon cations in argon‐matrix condensed phase experiments.