Structural and vibrational characterization of HCO+ and Rg-HCO+, Rg = {He, Ne, Ar, Kr, and Xe}.

The structures of the formyl ion (HCO+) and its rare gas tagged counterparts (Rg–HCO+, Rg = He, Ne, Ar, Kr, and Xe) were studied at the coupled-cluster singles, doubles, and perturbative triples [CCSD(T)]/aug-cc-pVTZ level of theory and basis set. A linear structure for these tagged complexes was predicted. The Rg binding energies for Rg–HCO+ are also examined at the CCSD(T) level. It was found that the binding interaction increases from He–HCO+ to Xe–HCO+. A multilevel potential energy surface built at the CCSD(T) and second-order Moller–Plesset perturbation levels of theory were used to study these species’ vibrational spectra. By changing the Rg in the first-solvation shell for HCO+, the Fermi resonance interaction between the first H+ bend overtone and the asymmetric and symmetric H–C–O stretches can be modulated. This Fermi resonance modulation is demonstrated by examining a series of rare gas solvated HCO+.