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08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
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Vibrational analysis of methyl cation-Rare gas atom complexes: CH3 +-Rg (Rg = He, Ne, Ar, Kr)
Jan Meisner1, Philipp P Hallmen1, Johannes Kästner1
1Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
The Journal of Chemical Physics
|March 3, 2019
Summary
The vibrational spectra of methyl cation-rare gas complexes show unsystematic trends due to significant zero-point energy effects, especially for helium. Tunneling effects in the methyl cation-helium complex are minimal for excited vibrational states.
Area of Science:
- Computational Chemistry
- Molecular Spectroscopy
- Quantum Chemistry
Background:
- Investigating the vibrational spectra of simple methyl cation-rare gas (CH3+-Rg) complexes provides insights into intermolecular interactions and zero-point energy effects.
- Previous studies on these complexes have yielded unsystematic results, highlighting the need for more consistent theoretical approaches.
Purpose of the Study:
- To theoretically study the vibrational spectra of CH3+-Rg (Rg = He, Ne, Ar, Kr) complexes using advanced computational methods.
- To introduce and apply configuration averaged vibrational self-consistent field (CA-VSCF) theory for a more consistent analysis of these sensitive systems.
- To investigate the occurrence and significance of tunneling effects in the CH3+-He complex.
Main Methods:
- Utilized vibrational configuration interaction (VCI) theory based on multidimensional potential energy surfaces (PESs) from coupled cluster calculations (CCSD(T)-F12a).
- Introduced and employed configuration averaged vibrational self-consistent field (CA-VSCF) theory for improved accuracy.
- Applied semiclassical instanton theory to assess tunneling splittings in the CH3+-He complex.
Main Results:
- Vibrational spectra calculations align with experimental findings, revealing unsystematic trends across the rare gas series.
- Significant zero-point vibrational energy effects were observed, particularly for the CH3+-He complex.
- Tunneling effects for the vibrational ground-state of CH3+-He were investigated, with calculations suggesting minimal tunneling for vibrationally excited states.
Conclusions:
- The study demonstrates the utility of VCI and CA-VSCF theories in elucidating the vibrational dynamics of CH3+-Rg complexes.
- Zero-point energy effects play a crucial role in the observed spectral trends.
- Tunneling contributions to vibrational spectra are likely negligible for excited states in the CH3+-He system.
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