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THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups

Ioppolo, S. and McGuire, B. A. and Allodi, M. A. and Blake, G. A. (2014) THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups. Faraday Discussions, 168 . pp. 461-484. ISSN 1359-6640.

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A fundamental problem in astrochemistry concerns the synthesis and survival of complex organic molecules (COMs) throughout the process of star and planet formation. While it is generally accepted that most complex molecules and prebiotic species form in the solid phase on icy grain particles, a complete understanding of the formation pathways is still largely lacking. To take full advantage of the enormous number of available THz observations (e.g., Herschel Space Observatory, SOFIA, and ALMA), laboratory analogs must be studied systematically. Here, we present the THz (0.3–7.5 THz; 10–250 cm^(−1)) and mid–IR (400–4000 cm^(−1)) spectra of astrophysically-relevant species that share the same functional groups, including formic acid (HCOOH) and acetic acid (CH_3COOH), and acetaldehyde (CH_3CHO) and acetone ((CH_3)_2CO), compared to more abundant interstellar molecules such as water (H_2O), methanol (CH_3OH), and carbon monoxide (CO). A suite of pure and mixed binary ices are discussed. The effects on the spectra due to the composition and the structure of the ice at different temperatures are shown. Our results demonstrate that THz spectra are sensitive to reversible and irreversible transformations within the ice caused by thermal processing, suggesting that THz spectra can be used to study the composition, structure, and thermal history of interstellar ices. Moreover, the THz spectrum of an individual species depends on the functional group(s) within that molecule. Thus, future THz studies of different functional groups will help in characterizing the chemistry and physics of the interstellar medium (ISM).

Item Type:Article
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URLURL TypeDescription
Ioppolo, S.0000-0002-2271-1781
McGuire, B. A.0000-0003-1254-4817
Allodi, M. A.0000-0002-3289-1659
Blake, G. A.0000-0003-0787-1610
Additional Information:© 2014 The Royal Society of Chemistry. Received 21st December 2013, Accepted 7th February 2014. First published online 07 Feb 2014. This work was supported by the NSF CRIF:ID and CSDM programs and the NASA Exobiology and Laboratory Astrophysics programs. The authors thank Coherent, Inc. for the loan of the Optical Parametric Amplifier used in these experiments. S.I. acknowledges support from a Niels Stensen Fellowship and a Marie Curie Fellowship (FP7-PEOPLE-2011-IOF-300957). B.A.M. gratefully acknowledges funding by an NSF Graduate Research Fellowship. M.A.A. was supported by the Department of Defense (DoD) Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. This article is part of themed collection: Astrochemistry of Dust, Ice and Gas.
Funding AgencyGrant Number
Niels Stensen FellowshipUNSPECIFIED
Marie Curie FellowshipFP7-PEOPLE-2011-IOF-300957
NSF Graduate Research FellowshipUNSPECIFIED
National Defense Science and Engineering Graduate (NDSEG) Fellowship32 CFR 168a
Record Number:CaltechAUTHORS:20140919-093132583
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Official Citation:THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups S. Ioppolo, B. A. McGuire, M. A. Allodi and G. A. Blake Faraday Discuss., 2014, 168, 461-484 DOI: 10.1039/C3FD00154G
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49848
Deposited By: Ruth Sustaita
Deposited On:19 Sep 2014 19:00
Last Modified:09 Mar 2020 13:18

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