Rotation of CH3+ Cations in Helium Droplets

Swetha Erukala; Deepak Verma; Andrey Vilesov

doi:10.1021/acs.jpclett.1c01274

Rotation of CH₃⁺ Cations in Helium Droplets

J Phys Chem Lett. 2021 Jun 3;12(21):5105-5109. doi: 10.1021/acs.jpclett.1c01274. Epub 2021 May 24.

Authors

Swetha Erukala¹, Deepak Verma¹, Andrey Vilesov^{1

2}

Affiliations

¹ Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
² Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States.

PMID: 34029088
DOI: 10.1021/acs.jpclett.1c01274

Abstract

Observation of the free rotation of molecules in helium droplets enabled microscopic study of interaction of quantum rotors with a superfluid environment at T = 0.4 K. This work extends studies of rotation in helium to molecular cations, such as methenium, CH₃⁺. The spectrum of the v₃ band of CH₃⁺ around 3130 cm^-1 has three prominent peaks assigned to the rotational structure of the band. While the free CH₃⁺ is an oblate top, in helium it behaves as a prolate top. This effect is ascribed to the strong binding of two He atoms along the figure axis of the ion. Our results indicate that the other He atoms within the first solvation shell remain fluxional and in disparity with the widely accepted model of a rigid He "snowball" surrounding ions.