CH3 internal rotation in 9-methylanthracene

Baba, Masaaki

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https://hdl.handle.net/2142/104573 Copy

Description

Title

CH3 internal rotation in 9-methylanthracene

Author(s)

Baba, Masaaki

Contributor(s)

• Hougen, Jon T.
• Misono, Masatoshi

Issue Date

2019-06-17

Keyword(s)

• Large amplitude motions
• Internal rotation

Abstract

We observed the rotationally resolved fluorescence excitation spectrum of the S$_1$ $\leftarrow$ S$_0$ transition of jet-cooled 9-methylanthracene. The potential energy curve for CH$_3$ internal rotation is six-fold symmetric. The barrier to rotation ($V_6$) is $\sim$ 120 cm$^{-1}$ [2], which is considerably larger than that of toluene ( $\sim$ 5 cm$^{-1}$ ) [1]. The $V_6$ value is the energy difference between two isomers {\textquoteleft}$staggered${\textquoteright} and {\textquoteleft}$eclipsed${\textquoteright}. The main contribution to $V_6$ is expected to be hyperconjugation, which is the $\pi$-like interaction between the aromatic $\pi$ orbital and methyl sp$^3$ orbital. The final goal of this work is to quantitatively elucidate the vibrational and rotational energy levels for CH$_3$ internal rotation. It is essential to observe the high-resolution and high-precision electronic spectra and theoretically search the best effective Hamiltonian to reproduce the experimental results. We are now developing a new laser control system with optical frequency comb locked to GPS, and an ab initio method which provides the reliable potential energy curve. \\[-1mm] \begin{flushleft} [1] M. Baba, et al., J. Phys. Chem. A {\bf 113}, 2369 (2009) \\[1mm] [2] D. R. Borst and D. W. Pratt, J. Chem. Phys. {\bf 113}, 3658 (2000) \end{flushleft}

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/104573

DOI

https://doi.org/10.15278/isms.2019.MI08

Copyright and License Information

Copyright 2019 Masaaki Baba

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