NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
High-Resolution IR Absorption Spectroscopy of Polycyclic Aromatic Hydrocarbons in the 3-micrometers Region: Role of PeripheryIn this work we report on high-resolution IR absorption studies that provide a detailed view on how the peripheral structure of irregular polycyclic aromatic hydrocarbons (PAHs) affects the shape and position of their 3-micrometers absorption band. To this purpose we present mass-selected, high-resolution absorption spectra of cold and isolated phenanthrene, pyrene, benz[a]antracene, chrysene, triphenylene, and perylene molecules in the 2950-3150 per cm range. The experimental spectra are compared with standard harmonic calculations, and anharmonic calculations using a modified version of the SPECTRO program that incorporates a Fermi resonance treatment utilizing intensity redistribution. We show that the 3-micrometers region is dominated by the effects of anharmonicity, resulting in many more bands than would have been expected in a purely harmonic approximation. Importantly, we find that anharmonic spectra as calculated by SPECTRO are in good agreement with the experimental spectra. Together with previously reported high-resolution spectra of linear acenes, the present spectra provide us with an extensive dataset of spectra of PAHs with a varying number of aromatic rings, with geometries that range from open to highly-condensed structures, and featuring CH groups in all possible edge configurations. We discuss the astrophysical implications of the comparison of these spectra on the interpretation of the appearance of the aromatic infrared 3-micrometers band, and on features such as the two-component emission character of this band and the 3-micrometers emission plateau.
Document ID
20170001939
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Maltseva, Elena
(Amsterdam Univ. Netherlands)
Petrignani, Annemieke
(Leiden Univ. Netherlands)
Candian, Alessandra
(Leiden Univ. Netherlands)
Mackie, Cameron J.
(Leiden Univ. Netherlands)
Huang, Xinchuan
(Search for Extraterrestrial Intelligence Inst. Mountain View, CA, United States)
Lee, Timothy J.
(NASA Ames Research Center Moffett Field, CA, United States)
Tielens, Alexander G. G. M.
(Leiden Univ. Netherlands)
Oomens, Jos
(Radboud Univ. Nijmegen, Netherlands)
Buma, Wybren Jan
(Amsterdam Univ. Netherlands)
Date Acquired
March 2, 2017
Publication Date
January 1, 2017
Publication Information
Publisher: AAS/IOP Publishing Partnership
Subject Category
Inorganic, Organic And Physical Chemistry
Optics
Report/Patent Number
ARC-E-DAA-TN37768
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
techniques: spectroscopic
astrochemistry | ISM: molecules
methods: laboratory
No Preview Available