Fermi resonance switching in KrH+Rg and XeH+Rg (Rg = Ne, Ar, Kr, and Xe)

Matrix isolation experiments have been successfully employed to extensively study the infrared spectrum of several proton-bound rare gas complexes. Most of these studies have focused on the spectral signature for the H+ stretch (nu (3)) and its combination bands with the intermolecular stretch coordinate (nu (1)). However, little attention has been paid to the Fermi resonance interaction between the H+ stretch (nu (3)) and H+ bend overtone (2 nu (2)) in the asymmetric proton-bound rare gas dimers, RgH(+)Rg '. In this work, we have investigated this interaction on KrH(+)Rg and XeH(+)Rg with Rg = (Ne, Ar, Kr, and Xe). A multilevel potential energy surface (PES) was used to simulate the vibrational structure of these complexes. This PES is a dual-level comprising of second-order MOller-Plesset perturbation theory and coupled-cluster singles doubles with perturbative triples [CCSD(T)] levels of ab initio theories. We found that when both the combination bands (n nu (1) + nu (3)) and bend overtone 2 nu (2) compete to borrow intensity from the nu (3) band, the latter wins over the former, which then results in the suppression of the n nu (1) + nu (3) bands. The current simulations offer new assignments for the ArH+Xe and KrH+Xe spectra. Complete basis set (CBS) binding energies for these complexes were also calculated at the CCSD(T)/CBS level.

Automated summary

Matrix isolation experiments have been used to study the infrared spectra of proton-bound rare gas complexes. However, little attention has been paid to the Fermi resonance interaction between the H+ stretch and bend overtone in asymmetric proton-bound rare gas dimers. This study investigates this interaction in KrH(+)Rg and XeH(+)Rg complexes, providing new assignments for their spectra and calculating binding energies at the CCSD(T)/CBS level.