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Title: POLYCYCLIC AROMATIC HYDROCARBONS WITH ARMCHAIR EDGES AND THE 12.7 μm BAND

In this Letter, we report the results of density functional theory calculations on medium-sized neutral polycyclic aromatic hydrocarbon (PAH) molecules with armchair edges. These PAH molecules possess strong C-H stretching and bending modes around 3 μm and in the fingerprint region (10-15 μm), and also strong ring deformation modes around 12.7 μm. Perusal of the entries in the NASA Ames PAHs Database shows that ring deformation modes of PAHs are common, although generally weak. Therefore, we propose that armchair PAHs with N{sub C} > 65 are responsible for the 12.7 μm aromatic infrared band in H II regions and discuss the astrophysical implications in the context of the PAH life cycle.
Authors:
;  [1] ;  [2]
  1. Leiden Observatory, Niels Bohrweg 2, 2333-CA Leiden (Netherlands)
  2. School of Chemistry, The University of Nottingham, Nottingham NG7 2RD (United Kingdom)
Publication Date:
OSTI Identifier:
22365365
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 791; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; DENSITY FUNCTIONAL METHOD; H2 REGIONS; INFRARED SPECTRA; LIFE CYCLE; MOLECULES; POLYCYCLIC AROMATIC HYDROCARBONS