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Paper: How to Build Pentagons and Heptagons from Hexagons around AGB Stars
Volume: 497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time
Page: 399
Authors: Öttl, S.; Huber, S. E.; Niederwanger, F.; Kimeswenger, S.
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are known to be one of the carriers of the ubiquitous aromatic infrared bands that are frequently observed in post-AGB stars and planetary nebulae (PNe). Although PAH features are identified in a wide variety of environments, the characteristics of the individual molecules are not clear so far. Several emission features are observed, but cannot be explained. Therefore a sophisticated understanding of all possible types and subtypes is required. This study presents a theoretical investigation of the IR spectra of PAHs containing (5,7)-member ring defects. Such defects consist of pentagons and heptagons instead of some of the hexagons usually constituting PAHs. Using density functional theory, the influence of the defects on the IR spectra of pyrene (C16H10) and coronene (C24H12) and their cations and anions were examined in detail. Additionally, the potential energy surface of the neutral species was explored.
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