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Rotation of CH3+ Cations in Helium Droplets
Swetha Erukala1, Deepak Verma1, Andrey Vilesov1,2
1Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
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.
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