Infrared Photodissociation Spectroscopy and Multireference Anharmonic Vibrational Study of the HO4+ Molecular Cation
Abstract
HO4+ has been proposed as an astrochemical sink of oxygen but has never been observed. Molecular cations of HO4+ and DO4+ are produced in a supersonic expansion. They are mass-selected, and their infrared photodissociation spectra are measured with the aid of argon-tagging. Previous theoretical studies have modeled these systems as proton-bound dimers of molecular oxygen. Several conformers were located on the quintet, triplet, and singlet surfaces, differing in energy by, at most, a few thousand wavenumbers; the singlet and triplet conformers have pronounced multiconfigurational character. Our HO4+ is formed in a relatively hot environment, and similar experiments have been shown capable of producing multiple conformers in low-lying electronic states. None of the predicted HO4+ isomers can be ruled out a priori based on energetic arguments. We interpret our spectra with second-order vibrational perturbation theory with resonances (VPT2+K) using quartic force fields based on an economical combination of single- and multi-reference theories. The VPT2+K simulations include the effect of electrical anharmonicity; this is particularly important for transitions involving the shared-proton stretch. Previously unidentified chain structures (H-O-O-O-O) that exist on the singlet and triplet surfaces likely represent the global minima.
Xavier, G. D.; Bernal-Uruchurtu, M. I.; Hernandez-Lamoneda, R., J. Chem. Phys. 2014, 141, 5, 081101. Xavier, F. G. D.; Hernandez-Lamoneda, R., PCCP 2015, 17, 16023-16032. Wagner, J. P.; McDonald, D. C.; Duncan, M. A., Angewandte Chemie-International Edition 2018, 57, 5081-5085.- Publication:
-
74th International Symposium on Molecular Spectroscopy
- Pub Date:
- June 2019
- DOI:
- 10.15278/isms.2019.WF06
- Bibcode:
- 2019isms.confEWF06F
- Keywords:
-
- Ions