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Onset of Rotational Decoupling for a Molecular Ion Solvated in Helium: From Tags to Rings and Shells
Julia A Davies1, Christoph Schran2, Fabien Brieuc2
1School of Chemistry, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom.
Physical Review Letters
|March 10, 2023
Summary
The study reveals how hydronium ions (H3O+) rotate differently when surrounded by helium-4 (4He) atoms. Adding more helium atoms causes distinct changes in rotation, but not due to superfluidity.
Area of Science:
- Physical Chemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Understanding the behavior of molecular ions in helium environments is crucial for studying solvation effects.
- The relationship between microscopic superfluidity and the rotational dynamics of ions in helium remains poorly understood.
Purpose of the Study:
- To investigate the rotational behavior of hydronium ions (H3O+) interacting with varying numbers of helium-4 (4He) atoms.
- To explore the influence of helium solvation on ion rotation and its connection to superfluid phenomena.
Main Methods:
- Infrared (IR) spectroscopy was employed to study helium-4 (4He)N⋯H3O+ complexes.
- Path integral simulations were conducted to complement experimental observations.
Main Results:
- Significant changes in the rotational behavior of H3O+ were observed as the number of 4He atoms increased.
- Rotational decoupling of the H3O+ core from the surrounding helium was evident for N>3.
- Abrupt shifts in rotational constants occurred at N=6 and N=12 helium atoms.
- Path integral simulations indicated that superfluid effects are not necessary to explain the observed rotational changes.
Conclusions:
- The solvation of H3O+ by 4He atoms leads to distinct changes in rotational dynamics.
- The observed phenomena can be explained without invoking incipient superfluid effects, differentiating these findings from studies on neutral molecules.
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