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          Institute: Fritz-Haber-Institut     Collection: Molecular Physics     Display Documents

ID: 39090.0, Fritz-Haber-Institut / Molecular Physics
Laboratory Infrared Spectroscopy of Cationic Polycyclic Aromatic Hydrocarbon Molecules
Authors:Oomens, Jos; Tielens, A.G.G.M.; Sartakov, Boris G.; Helden, Gert von; Meijer, Gerard
Date of Publication (YYYY-MM-DD):2003-07-20
Title of Journal:The Astrophysical Journal
Journal Abbrev.:ApJ
Issue / Number:2
Start Page:968
End Page:985
Copyright:2003. The American Astronomical Society.
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Infrared spectroscopy of a variety of interstellar sources shows strong mid-IR emission bands, which are generally attributed to emission from highly vibrationally excited polycyclic aromatic hydrocarbon molecules (PAHs) in the neutral and, particularly, cationic states. Over the past decade, various experimental methods have been developed to record the infrared spectra of cationic PAHs in the laboratory. In this paper, we discuss available experimental spectra obtained with matrix isolation spectroscopy (MIS), infrared multiple-photon dissociation of trapped ions (MPD), dissociation spectroscopy of ionic PAH van der Waals clusters (VDW), and infrared emission (IRE). Moreover, we compare these experimental spectra to density functional theory (DFT) calculations. The main body of experimental data relies on MIS and MPD spectra, and we present a detailed comparison of results from these methods, providing linear and multiple-photon absorption data, respectively. The effects of multiple-photon absorption, as encountered in MPD, and multiple-photon emission, occurring in interstellar spectra, are carefully assessed with the use of mathematical models, which include the effects of vibrational anharmonicity. We show that an analysis of the multiple-photon and linear data can provide important information on the anharmonicity parameters, which is otherwise difficult to attain. This is illustrated with a detailed comparison of the linear and multiple-photon absorption spectra of the naphthalene cation, yielding experimental anharmonicity parameters for the IR-active modes in the 5001700 cm-1 range.
External Publication Status:published
Document Type:Article
Communicated by:Gerard Meijer
Affiliations:Fritz-Haber-Institut/Molecular Physics
External Affiliations:FOM Institute for Plasma Physics "Rijnhuizen," Nieuwegein, Netherlands; Kapteyn Institute, University of Groningen, Groningen, Netherlands;
General Physics Institute, Moscow, Russia;
Department of Molecular and Laser Physics, University of Nijmegen, The Netherlands.
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