Multidimensional Tunneling In 2-nitrotoluenea

Coudert, L. H.

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https://hdl.handle.net/2142/116511 Copy

Description

Title

Multidimensional Tunneling In 2-nitrotoluenea

Author(s)

Coudert, L. H.

Contributor(s)

• Goubet, Manuel
• Cuisset, Arnaud
• Roucou, Anthony

Issue Date

2022-06-24

Keyword(s)

Mini-symposium: Benchmarking in Spectroscopy

Abstract

Although many non-rigid molecules displaying a single LAM have been spectroscopically characterized, less results are available about non-rigid molecules displaying several LAMs, as they are theoretically more challenging.\footnotetext[1]{This work received financial support from the French ANR. Project METIS under contract number ANR-20-ASTR-0016-03} This is confirmed by a recent spectroscopic investigation of nitrotoluene$^b$\footnotetext[2]{Roucou, Goubet, Kleiner, Bteich and Cuisset, {\em ChemPhysChem}~{\bf 21} (2020) 1} which revealed that its 2-nitrotoluene isomeric species displays two LAMs corresponding to internal rotations of the CH$_3$ and NO$_2$ groups. In this investigation,$^b$ because no approach accounting for two LAMs was available, the microwave spectrum of 2-nitrotoluene was analyzed using a simplified approach accounting only for the torsional motion of the CH$_3$ group. In this talk, the IAM water dimer formalism$^c$\footnotetext[3]{Hougen, {\em J.\ Mol.\ Spec.}~{\bf 114} (1985) 395; and Coudert and Hougen, {\em J.\ Mol.\ Spec.}~{\bf 130} (1988) 86} will be applied to 2-nitrotoluene. As this theoretical approach is designed for multidimensional tunneling in the high-barrier limit, it is well suited for this species. Once the equilibrium configurations and the tunneling paths are chosen, the IAM approach$^c$ allows us to derive a fitting Hamiltonian accounting for the rotational dependence of the tunneling splittings, but not for their magnitude, which should be obtained fitting the spectroscopic data. In 2-nitrotoluene, there are six $C_1$ symmetry equilibrium configurations and two tunneling paths. The first and most feasible one corresponds to a $2\pi/3$ rotation of the methyl group. The second one is the complicated geared internal rotation of both the CH$_3$ and NO$_2$ groups identified using quantum chemistry calculations.$^b$ The results of the line position analysis of the available microwave data$^b$ with the new IAM approach will be presented. It is hoped that the analysis results will be more satisfactory than with the simplified approach$^b$ and this will provide us with a better understanding of the 2-nitrotoluene multidimensional potential energy surface.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116511

DOI

https://doi.org/10.15278/isms.2022.FB04

Copyright and License Information

Copyright 2022 held by the authors

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