ROTATIONAL STRUCTURE OF THE IR/FIR BANDS OF SMALL PAHS
Loading...
Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Accurate spectroscopic measurements in the laboratory of PAH molecules are required to better understand their excitation/relaxation processes which could be responsible for the Unidentified Infrared Bands observed in various objects in space. In particular very few is known concerning the rotational structure of the IR/FIR bands of PAHs. We used the high resolution Fourier Transform interferometer of the AILES beamline of synchrotron SOLEIL to record the rotationally resolved spectra of several IR/FIR vibrational modes of naphthalene (C$_{10}$H$_{8}$) and its derivatives: quinoline (C$_9$H$_7$N), isoquinoline (C$_9$H$_7$N), azulene (C$_{10}H_{8}$), quinoxaline (C$_8$H$_6$N$_2$), quinazoline (C$_8$H$_6$N$_2$). Firstly, the intense band associated with the $\nu_{46}$ CH bending out of plane mode of naphthalene recorded under jet conditions (Jet-AILES experiment developed on the AILES beamline by the IPR-LADIR-PhLAM consortium) revealed transitions involving low J and Ka rotational quantum numbers. These new data permitted to accurately fit the ground state rotational constants and to improve the $\nu_{46}$ band constants, 51 (2011)}. As a second step, we performed the rotational analysis of the low frequency $\nu_{47}$ and $\nu_{48}$ bands of naphthalene recorded at room-temperature in the long absorption pathlength cell from ISMO. As a last step, the high resolution spectra of several bands of azulene, quinoline, isoquinoline and quinoxaline were recorded at room temperature and analyzed using the same procedure. All the rotational constants fitted in the present work were compared to the results of anharmonic DFT calculations realized at various levels of accuracy.
Description
Author Institution: Ligne AILES, Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif sur Yvette Cedex - France; Laboratoire de Physique des Lasers, Atomes et Molecules, UMR 8523 CNRS - Universite Lille 1, Batiment P5, F-59655 Villeneuve d'Ascq Cedex, France; Universite de Rennes 1, Institut de Physique de Rennes, CNRS, UMR 6251, F-35042 Rennes Cedex, France; UPMC Universite Paris 06, UMR 7075 CNRS, Laboratoire de Dynamique, Interactions et Reactivite (LADIR), F-75005, Paris, France