Visible Photodissociation Spectra Of The 1-methyl And 2-methylnaphthalene Cations: Laser Spectroscopy And Theoretical Simulations

Brechignac, Philippe

Permalink

https://hdl.handle.net/2142/50858 Copy

Description

Title

Visible Photodissociation Spectra Of The 1-methyl And 2-methylnaphthalene Cations: Laser Spectroscopy And Theoretical Simulations

Author(s)

Brechignac, Philippe

Contributor(s)

• Dhaouadi, Zoubeida
• Schmidt, Timothy
• Troy, Tyler
• Pino, Thomas
• Parneix, Pascal
• Falvo, Cyril
• Feraud, Geraldine
• Friha, Hela

Issue Date

2014-06-18

Keyword(s)

Mini-symposium: Beyond the Mass-to-Charge Ratio: Spectroscopic Probes of the Structures of Ions

Abstract

Naphthalene (Np) and its methylated derivatives (1-Me-Np and 2-Me-Np) are prototype molecules for spectroscopists as first members of the polycyclic aromatic hydrocarbons (PAHs) family. High resolution studies are capable to explore the details of the internal rotation of the methyl group. Although this was achieved in neutral PAHs\footnote{see for instance Baba et al, \emph{J.Phys.Chem.A}, \textbf{2009}, 113, 2366}, the task is not the same in cations. Me-Np cations have been probed by resonance-enhanced multiphoton dissociation\footnote{Dunbar et al, \emph{J. Am. Chem. Soc.} \textbf{1976}, 98, 7994-7999 and \emph{J.Phys.Chem.} \textbf{1985}, 89, 3617}, showing only very broad and unresolved spectra, while absorption in argon matrix revealed more resolved vibronic bands\footnote{Andrews et al, \emph{J.Phys.Chem.} \textbf{1982}, 86, 2916}. The electronic absorption gas phase spectra of 1-Me-Np$^+$ and 2-Me-Np$^+$ were measured using an Ar-tagging technique. In both cases, a band system was observed in the visible range and assigned to the $D_2\leftarrow D_0$ transition. The 1-Me-Np$^+$ absorption bands revealed a red shift of 808 cm$^{-1}$, relative to Np$^+$ (14 906 cm$^{-1}$)\footnote{Pino et al, \emph{J. Chem. Phys.} \textbf{1999}, 111, 7337-7347} , while for 2-Me-Np$^+$ a blue shift of 226 cm$^{-1}$ was found. A short vibrational progression was also observed. Moreover, insights into the internal rotation motion of the CH$_3$ were inferred, although intrinsic broadening due to intramolecular relaxation was present. These measurements were supported by detailed quantum chemical calculations that allowed exploration of the potential energy curves, along with a complete simulation of the harmonic FC factors using the cumulant Gaussian fluctuations formalism, extended to include the internal rotation.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/50858

DOI

https://doi.org/10.15278/isms.2014.WG02

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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