Infrared spectroscopy of H+(CO)2 in the gas phase and in para-hydrogen matrices

• Published in: The Journal of chemical physics 2020-08, Vol.153 (8), p.084305-084305
• Main Authors: Leicht, Daniel, Rittgers, Brandon M., Douberly, Gary E., Wagner, J. Philipp, McDonald, David C., Mauney, Daniel T., Tsuge, Masashi, Lee, Yuan-Pern, Duncan, Michael A.
• Format: Article
• Language: English
• Subjects: Absorption spectra; Anharmonicity; Argon; Carbon monoxide; Dimers; Electron bombardment; Fourier transforms; FTIR spectrometers; Hydrogen; Hydrogen storage; Infrared lasers; Infrared spectroscopy; Ion bombardment; Irradiation; Isomers; Marking; Molecular beams; Molecular ions; Neon; Photodissociation; Physics; Protons; Spectrum analysis; Vapor phases
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/5.0019731

The H+(CO)2 and D+(CO)2 molecular ions were investigated by infrared spectroscopy in the gas phase and in para-hydrogen matrices. In the gas phase, ions were generated in a supersonic molecular beam by a pulsed electrical discharge. After extraction into a time-of-flight mass spectrometer, the ions were mass selected and probed by infrared laser photodissociation spectroscopy in the 700 cm−1–3500 cm−1 region. Spectra were measured using either argon or neon tagging, as well as tagging with an excess CO molecule. In solid para-hydrogen, ions were generated by electron bombardment of a mixture of CO and hydrogen, and absorption spectra were recorded in the 400 cm−1–4000 cm−1 region with a Fourier-transform infrared spectrometer. A comparison of the measured spectra with the predictions of anharmonic theory at the CCSD(T)/ANO1 level suggests that the predominant isomers formed by either argon tagging or para-hydrogen isolation are higher lying (+7.8 kcal mol−1), less symmetric isomers, and not the global minimum proton-bound dimer. Changing the formation environment or tagging strategy produces other non-centrosymmetric structures, but there is no spectroscopic evidence for the centrosymmetric proton-bound dimer. The formation of higher energy isomers may be caused by a kinetic effect, such as the binding of X (=Ar, Ne, or H2) to H+(CO) prior to the formation of X H+(CO)2. Regardless, there is a strong tendency to produce non-centrosymmetric structures in which HCO+ remains an intact core ion.