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Infrared Spectroscopy of CH5+ Cations in Helium Nanodroplets
Amandeep Singh1, Sofia H Allison1,2, Andrew Abishek A Azhagesan3
1Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
Abstract:
The methanium CH5+ is a prototypical fluxional ion whose infrared spectra remain unassigned. Here we report on the infrared spectra of CH5+ cations and its deuterated isotopomer, CH4D+, in helium droplets at a low temperature of 0.38 K. The ions were produced upon protonation of CH4 molecules, a technique that was developed in this work. The spectra of CH5+ around 3000 cm-1 show two strong and broad infrared bands and a weak shoulder, reflecting its highly fluxional nature. The spectrum of CH4D+ shows a much sharper infrared band, indicating a partial quenching of the exchange of H/D atoms. This work also reports on the infrared spectrum of the methane dimer radical cations (CH4)2+.
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