Torsion - Vibration Coupling In The Methyl Rotor Systems

Huang, Meng

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https://hdl.handle.net/2142/51101 Copy

Description

Title

Torsion - Vibration Coupling In The Methyl Rotor Systems

Author(s)

Huang, Meng

Contributor(s)

• Miller, Terry A.
• McCoy, Anne B.

Issue Date

2014-06-19

Keyword(s)

Large amplitude motions, internal rotation

Abstract

The couplings between the CH stretch and CH${_3}$ torsion in the methyl rotor have been widely studied in methanol.\footnote{D.~S.~Perry \textit{J.~Mol.~Spectpsc.} 2009, 257, 1-10} In this research, we are focusing on the effect of this coupling on the vibrational spectrum in the CH stretch region of the methanol cation - argon cluster, CH${_3}$OH${^+}$${\cdot}$Ar, and the methyl peroxy radical, CH${_3}$OO${\cdot}$. A reduced dimensional analysis including the three CH stretches and the CH${_3}$ torsion is used to calculate the spectra. The CH stretches are treated as harmonic oscillators whose frequency depends on the torsional angle because of coupling between the CH stretch and CH${_3}$ torsion. The infrared spectrum of CH${_3}$OH${^+}$${\cdot}$Ar cluster taken by the Duncan group\footnote{J.~D.~Mosley, J.~W.~Young, M.~A.~Duncan \textit{68th International Symosium of Molecular Spectroscopy}} shows multiple peak structure in the CH stretch region. In this system, the calculation indicates the coupling between the CH${_3}$ torsion and CH stretch is relatively strong. The multiple peak structure in the experimental spectrum can be assigned to the CH stretch fundamentals and the combination band involving the CH stretch and the CH${_3}$ torsion. However, for the methyl peroxy radical, the calculated coupling is very weak. In the CH stretch region of the infrared spectrum of CH${_3}$OO${\cdot}$ taken by the Lee group\footnote{K.-H.~Hsu, Y.-P.~Lee, M.~Huang, T.~A.~Miller \textit{68th International Symosium of Molecular Spectroscopy}}, only CH stretch fundamentals with relatively broad rotational contours are observed. The broadened structure of the CH stretch fundamental is possibly caused by sequence band structure from low lying torsional levels which are well populated and shift very little from the origin band.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/51101

DOI

https://doi.org/10.15278/isms.2014.RJ08

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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