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The NASA Ames PAH IR Spectroscopic Database and thefar-IR

Published online by Cambridge University Press:  30 March 2011

C. Joblin ,
A.G.G.M. Tielens ,
C. Boersma ,
L.J. Allamandola ,
C.W. Bauschlicher Jr. ,
A. Ricca ,
J. Cami ,
E. Peeters ,
F. Sánchez de Armas  and
G. Puerta Saborido
...Show all authors
C. Boersma
Affiliation:
NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035, USA. e-mail: [email protected]
L.J. Allamandola
Affiliation:
NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035, USA. e-mail: [email protected]
C.W. Bauschlicher Jr.
Affiliation:
NASA Ames Research Center, MS 230-3, Moffett Field, CA 94035, USA
A. Ricca
Affiliation:
NASA Ames Research Center, MS 230-3, Moffett Field, CA 94035, USA
J. Cami
Affiliation:
Department of Physics and Astronomy, PAB 213, The University of Western Ontario, London, ON N6A 3K7, Canada
E. Peeters
Affiliation:
Department of Physics and Astronomy, PAB 213, The University of Western Ontario, London, ON N6A 3K7, Canada
F. Sánchez de Armas
Affiliation:
SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA
G. Puerta Saborido
Affiliation:
SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA
A.L. Mattioda
Affiliation:
NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035, USA. e-mail: [email protected]
D.M. Hudgins
Affiliation:
NASA Headquarters, MS 3Y28, 300 E St. SW, Washington, DC 20546, USA

Abstract

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Polycyclic Aromatic Hydrocarbons (PAHs) are widespread across the Universe and influencemany stages of the Galactic lifecycle. The presence of PAHs has been well established andthe rich mid-IR PAH spectrum is now commonly used as a probe into (inter)stellarenvironments. The NASA Ames PAH IR Spectroscopic Database has been key to test and refinethe “PAH hypothesis”. This database is a large coherent set (>600 spectra) oflaboratory measured and DFT computed infrared spectra of PAHs fromC10H8 to C130H28 and has been made availableon the web at (http://www.astrochem.org/pahdb). With a new spectral window opening up; thefar-IR, the study of PAH far-IR spectra and the quest for identifying aunique member of the interstellar PAH family has begun. To guide this research, the far-IR(>20 μm) spectra of different sets of PAHs are investigatedusing the NASA Ames PAH IR Spectroscopic Database. These sets explore the influence ofsize, shape, charge and composition on the far-IR PAH spectrum. The far-IR is also thedomain of the so-called “drumhead” modes and other molecular vibrations involving loworder bending vibrations of the carbon skeleton as a whole. As with drums, these aremolecule and shape specific and promise to be a key diagnostic for specific PAHs. Here,the sensitivity of these “drumhead” modes to size and shape is assessed by comparing thefrequencies of the lowest drumhead modes of a family of circular shaped (the coronene“family”) and rhombus shaped (the pyrene “family”) PAH molecules. From this study, someconsequences for an observing strategy are drawn.

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 46: PAHs and the Universe: A Symposium to Celebrate the 25thAnniversary of the PAH Hypothesis , 2011 , pp. 109 - 115
Copyright
© EAS, EDP Sciences 2011

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