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Infrared Spectra of Protonated Coronene and Its Neutral Counterpart in Solid Parahydrogen: Implications for Unidentified Interstellar Infrared Emission Bands
Author(s) -
Bahou Mohammed,
Wu YuJong,
Lee YuanPern
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201308971
Subject(s) - coronene , protonation , infrared , infrared spectroscopy , chemistry , photochemistry , dissociation (chemistry) , spectral line , spin isomers of hydrogen , pyrene , emission spectrum , analytical chemistry (journal) , molecule , hydrogen , physics , organic chemistry , astronomy , ion
Large protonated polycyclic aromatic hydrocarbons (H + PAHs) are possible carriers of unidentified infrared (UIR) emission bands from interstellar objects, but the characterization of infrared (IR) spectra of large H + PAHs in the laboratory is challenging. IR absorption spectra of protonated coronene (1‐C 24 H 13 + ) and mono‐hydrogenated coronene (1‐C 24 H 13 . ), which were produced upon electron bombardment of parahydrogen containing a small proportion of coronene (C 24 H 12 ) during matrix deposition, were recorded. The spectra are of a much higher resolution than those obtained by IR multiphoton dissociation by Dopfer and co‐workers. The IR spectra of protonated pyrene and coronene collectively appear to have the required chromophores for features of the UIR bands, and the spectral shifts on an increase in the number of benzenoid rings point in the correct direction towards the positions of the UIR bands. Larger protonated peri‐condensed PAHs might thus be key species among the carriers of UIR bands.