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Title: The ir emission features: Emission from PAH (Polycyclic Aromatic Hydrocarbons) molecules and amorphous carbon particles

Abstract

PAHs can have several forms in the interstellar medium. To assess the importance of each requires the availability of a collection of high quality, complete mid-ir interstellar emission spectra, a collection of laboratory spectra of PAH samples prepared under realistic conditions and a firm understanding of the microscopic emission mechanism. Given what we currently know about PAHs, the spectroscopic data suggests that there are at least two components which contribute to the interstellar emission spectrum: free molecule sized PAHs producing the narrow features and amorphous carbon particles (which are primarily made up of an irregular ''lattice'' of PAHs) contributing to the broad underlying components. An exact treatment of the ir fluorescence from highly vibrationally excited large molecules shows that species containing between 20 and 30 carbon atoms are responsible for the narrow features, although the spectra match more closely with the spectra of amorphous carbon particles. Since little is known about the spectroscopic properties of free PAHs and PAH clusters, much laboratory work is called for in conjunction with an observational program which focuses on the spatial characteristics of the spectra. In this way the distribution and evolution of carbon from molecule to particle can be traced. 38 refs., 9more » figs.« less

Authors:
; ;
Publication Date:
Research Org.:
National Aeronautics and Space Administration, Moffett Field, CA (USA). Ames Research Center; Michigan Univ., Ann Arbor (USA). Dept. of Atmospheric and Oceanic Science
OSTI Identifier:
6581763
Report Number(s):
CONF-8602110-1
ON: DE87003377
DOE Contract Number:  
FG02-85ER13442
Resource Type:
Conference
Resource Relation:
Conference: Conference on polycyclic aromatic hydrocarbons and astrophysics, Les Houches, France, 1 Feb 1986
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; INTERSTELLAR SPACE; POLYCYCLIC AROMATIC HYDROCARBONS; INFRARED SPECTRA; COSMIC GASES; EMISSION SPECTRA; EXPERIMENTAL DATA; AROMATICS; DATA; FLUIDS; GASES; HYDROCARBONS; INFORMATION; NUMERICAL DATA; ORGANIC COMPOUNDS; SPACE; SPECTRA; 640101* - Astrophysics & Cosmology- Cosmic Radiation

Citation Formats

Allamandola, L J, Tielens, A G.G.M., and Barker, J R. The ir emission features: Emission from PAH (Polycyclic Aromatic Hydrocarbons) molecules and amorphous carbon particles. United States: N. p., 1986. Web.
Allamandola, L J, Tielens, A G.G.M., & Barker, J R. The ir emission features: Emission from PAH (Polycyclic Aromatic Hydrocarbons) molecules and amorphous carbon particles. United States.
Allamandola, L J, Tielens, A G.G.M., and Barker, J R. 1986. "The ir emission features: Emission from PAH (Polycyclic Aromatic Hydrocarbons) molecules and amorphous carbon particles". United States. https://www.osti.gov/servlets/purl/6581763.
@article{osti_6581763,
title = {The ir emission features: Emission from PAH (Polycyclic Aromatic Hydrocarbons) molecules and amorphous carbon particles},
author = {Allamandola, L J and Tielens, A G.G.M. and Barker, J R},
abstractNote = {PAHs can have several forms in the interstellar medium. To assess the importance of each requires the availability of a collection of high quality, complete mid-ir interstellar emission spectra, a collection of laboratory spectra of PAH samples prepared under realistic conditions and a firm understanding of the microscopic emission mechanism. Given what we currently know about PAHs, the spectroscopic data suggests that there are at least two components which contribute to the interstellar emission spectrum: free molecule sized PAHs producing the narrow features and amorphous carbon particles (which are primarily made up of an irregular ''lattice'' of PAHs) contributing to the broad underlying components. An exact treatment of the ir fluorescence from highly vibrationally excited large molecules shows that species containing between 20 and 30 carbon atoms are responsible for the narrow features, although the spectra match more closely with the spectra of amorphous carbon particles. Since little is known about the spectroscopic properties of free PAHs and PAH clusters, much laboratory work is called for in conjunction with an observational program which focuses on the spatial characteristics of the spectra. In this way the distribution and evolution of carbon from molecule to particle can be traced. 38 refs., 9 figs.},
doi = {},
url = {https://www.osti.gov/biblio/6581763}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1986},
month = {Wed Jan 01 00:00:00 EST 1986}
}

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