Trihydrogen Cation with Neon and Argon: Structural, Energetic, and Spectroscopic Data from Quartic Force Fields

The argonium cation, ArH⁺, has been previously detected in nature for the first time. This cation is believed to form through the gas-phase reaction of Ar⁺ and H₂. In this work, quantum chemical techniques show that the reaction of Ar and H₃⁺ may be a viable alternative or contributor to the creation of ArH⁺ corroborating previous analysis. In order to further evaluate this claim, highly accurate quartic force field computations are used to produce spectroscopic data and anharmonic vibrational frequencies for ArH₃⁺ in its 18 isotopologues. NeH₃⁺ is also analyzed but has a low Ne–H₃⁺ dissociation barrier. Therefore, it less likely to be observed. Consequently, NeH⁺ is also unlikely to be formed from NeH₃⁺ as it was also not from NeH₂<sup>+